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  • 1990-1994  (1,339)
  • 1985-1989
  • 1992  (1,339)
  • Engineering  (757)
  • Computational Chemistry and Molecular Modeling  (582)
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Years
  • 1990-1994  (1,339)
  • 1985-1989
Year
  • 1
    Electronic Resource
    Electronic Resource
    Chichester [u.a.] : Wiley-Blackwell
    International Journal of Numerical Modelling: Electronic Networks, Devices and Fields 5 (1992), S. 275-288 
    ISSN: 0894-3370
    Keywords: Engineering ; Electrical and Electronics Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Electrical Engineering, Measurement and Control Technology
    Notes: This paper presents the simulation of a class of MIMD systems using discrete-event simulation enhanced by graphics-oriented reporting. MIMD systems can be specified, modelled and simulated using the package and in turn provide estimates of certain performance indices. A multiserver queueing model is constructed to describe the flow of data and instructions through the various elements of the system. The model is composed of P processors sharing M memory modules through a user-defined interconnection network. Graphical outputs allow the user to view the state of every processor/memory module over the simulation time with performance estimates such as the relative speedup, throughput, and utilization factor. Moreover, system performance graphs as a function of various system parameters are obtained to indicate the expected system behaviour for various loads and system configurations. The results section shows a case study of the influence of the memory modules' access time on the system performance. The purpose of the results is to aid in the analysis, understanding, design, and performance prediction of a class of MIMD systems in a user-friendly environment.
    Additional Material: 15 Ill.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Chichester [u.a.] : Wiley-Blackwell
    International Journal of Numerical Modelling: Electronic Networks, Devices and Fields 5 (1992), S. 83-92 
    ISSN: 0894-3370
    Keywords: Engineering ; Electrical and Electronics Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Electrical Engineering, Measurement and Control Technology
    Notes: The permeability tensor of the homogeneous bulk material externally equivalent to a laminated packet of non-linear, anisotropic, non-hysteretic sheets is derived by symbolic computation. The composite permeability bears a surprisingly simple algebraic relationship to the local permeabilities of its component materials even in the general case. Several special cases of common interest, where the tensor permeability assumes symmetric or diagonal form, are examined. Results are presented both as algebraic expressions and as brief optimized Fortran subroutines suitable for fitting into field analysis programs.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Chichester [u.a.] : Wiley-Blackwell
    International Journal of Numerical Modelling: Electronic Networks, Devices and Fields 5 (1992), S. 111-120 
    ISSN: 0894-3370
    Keywords: Engineering ; Electrical and Electronics Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Electrical Engineering, Measurement and Control Technology
    Notes: In this paper, the method of transmission-line modelling is used to determine the transient response of a lossy transmission line. Non-linearity and frequency-dependent parameters (R and G) can be included without undue difficulty. Several numerical examples are described and are compared with exact and/or experimental results. In all cases good agreements are obtained.
    Additional Material: 11 Ill.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Chichester [u.a.] : Wiley-Blackwell
    International Journal of Numerical Modelling: Electronic Networks, Devices and Fields 5 (1992), S. 139-139 
    ISSN: 0894-3370
    Keywords: Engineering ; Electrical and Electronics Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Electrical Engineering, Measurement and Control Technology
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    Chichester [u.a.] : Wiley-Blackwell
    International Journal of Numerical Modelling: Electronic Networks, Devices and Fields 5 (1992), S. 121-127 
    ISSN: 0894-3370
    Keywords: Engineering ; Electrical and Electronics Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Electrical Engineering, Measurement and Control Technology
    Notes: A random flight model of linear transport processes in two spatial dimensions is considered and solved exactly in closed algebraic form. Its one-dimensional version had been proposed by Taitel as a means to overcome the paradox of infinite speed of propagation within classical heat diffusion theory. The connection with hyperbolic diffusion theory is complemented here by deriving the discrete fluxes and their relaxation term. Moreover, such an approach circumvents the discretization of a continuum model for an intrinsically discrete process, when diffusion processes are to be solved numerically. Finite samples are treated by means of the reflection method. Some applications of these general results are mentioned.
    Additional Material: 3 Ill.
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  • 6
    Electronic Resource
    Electronic Resource
    Chichester [u.a.] : Wiley-Blackwell
    International Journal of Numerical Modelling: Electronic Networks, Devices and Fields 5 (1992), S. 143-144 
    ISSN: 0894-3370
    Keywords: Engineering ; Electrical and Electronics Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Electrical Engineering, Measurement and Control Technology
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    Chichester [u.a.] : Wiley-Blackwell
    International Journal of Numerical Modelling: Electronic Networks, Devices and Fields 5 (1992), S. 149-161 
    ISSN: 0894-3370
    Keywords: Engineering ; Electrical and Electronics Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Electrical Engineering, Measurement and Control Technology
    Notes: Under wideband and especially ultrawideband (short pulse) excitation, the electromagnetic fields, after encounters with a propagation or scattering environment, reveal features which range from highly resolved spikes or dips to smooth oscillations at early and late observation times, respectively. Time-domain (TD) analytic modelling should be structured around wave objects which relate features (observables) in data to distinct features in the environment. A strategy to this end, named observable-based parametrization (OBP), is proposed here. The rules are learned from frequency- and time-domain asymptotics applies to spatial and spectral domain representations of tractable prototype problems. This leads to self-consistent hybrid combinations OBP-TD travelling (wavefront) and oscillatory (resonant) synthesizing basis fields; the latter include novel TD leaky modes for guiding wave channels and TD Bragg modes for periodic arrays. These concepts are illustrated by examples.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    Chichester [u.a.] : Wiley-Blackwell
    International Journal of Numerical Modelling: Electronic Networks, Devices and Fields 5 (1992), S. 183-201 
    ISSN: 0894-3370
    Keywords: Engineering ; Electrical and Electronics Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Electrical Engineering, Measurement and Control Technology
    Notes: An approach for numerically integrating the partial differential equations describing passive physical systems consists in modelling the continuous-domain physical system by means of a passive discrete-domain system. As has recently been shown, this can be achieved, in particular also for Maxwell's equations, by means of the same principles as known from multidimensional wave digital filters, which offers a number of important advantages. The present paper deals specifically with the application of the approach to Maxwell's equations and supplements corresponding results previously published.
    Additional Material: 12 Ill.
    Type of Medium: Electronic Resource
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  • 9
    Electronic Resource
    Electronic Resource
    Chichester [u.a.] : Wiley-Blackwell
    International Journal of Numerical Modelling: Electronic Networks, Devices and Fields 5 (1992), S. 203-218 
    ISSN: 0894-3370
    Keywords: Engineering ; Electrical and Electronics Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Electrical Engineering, Measurement and Control Technology
    Notes: There is an increasing interest in the numerical modelling of physical and biological processes using cellular automata or cellular systems. One of the main advantages in using the concept of cellular systems is the inherent high degree of parallelism. The purpose of the contribution is to formally relate two different areas: time-domain modelling of physical processes using cellular systems and massive parallel implementations. At first, an overview of applications of cellular systems in computation theory and in modelling of physical systems and an overview of implementations of cellular systems is given. The subsequent sections address the following two questions: (1) Which class of algorithms can be interpreted as cellular systems. (2) Can cellular systems be efficiently simulated on a given parallel architecture. Results concerning these issues are presented.
    Additional Material: 10 Ill.
    Type of Medium: Electronic Resource
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  • 10
    Electronic Resource
    Electronic Resource
    Chichester [u.a.] : Wiley-Blackwell
    International Journal of Numerical Modelling: Electronic Networks, Devices and Fields 5 (1992), S. 163-182 
    ISSN: 0894-3370
    Keywords: Engineering ; Electrical and Electronics Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Electrical Engineering, Measurement and Control Technology
    Notes: An overview is given on the application of finite difference time-domain analysis techniques to the simulation of electromagnetic wave phenomena and the design of planar microwave integrated circuits. In particular the application to the analysis of three-dimensional discontinuities in coplanar microwave circuits is described and numerical and experimental results are presented. Finally the design of planar microwave circuits containing non-linear active components using the finite difference time-domain method in combination with a harmonic balance technique is demonstrated using an example of a LUFET circuit.
    Additional Material: 17 Ill.
    Type of Medium: Electronic Resource
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  • 11
    Electronic Resource
    Electronic Resource
    Chichester [u.a.] : Wiley-Blackwell
    International Journal of Numerical Modelling: Electronic Networks, Devices and Fields 5 (1992) 
    ISSN: 0894-3370
    Keywords: Engineering ; Electrical and Electronics Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Electrical Engineering, Measurement and Control Technology
    Type of Medium: Electronic Resource
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  • 12
    Electronic Resource
    Electronic Resource
    Chichester [u.a.] : Wiley-Blackwell
    International Journal of Numerical Modelling: Electronic Networks, Devices and Fields 5 (1992), S. i 
    ISSN: 0894-3370
    Keywords: Engineering ; Electrical and Electronics Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Electrical Engineering, Measurement and Control Technology
    Type of Medium: Electronic Resource
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  • 13
    Electronic Resource
    Electronic Resource
    Chichester [u.a.] : Wiley-Blackwell
    International Journal of Numerical Modelling: Electronic Networks, Devices and Fields 5 (1992), S. 251-257 
    ISSN: 0894-3370
    Keywords: Engineering ; Electrical and Electronics Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Electrical Engineering, Measurement and Control Technology
    Notes: This paper details general expressions for implementing timestep transformations in transmission-line matrix (TLM) modelling of diffusion processes. The expressions can be conveniently incorporated into any TLM routine which models multidimensional problems using a variable meshing technique.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
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  • 14
    Electronic Resource
    Electronic Resource
    Chichester [u.a.] : Wiley-Blackwell
    International Journal of Numerical Modelling: Electronic Networks, Devices and Fields 5 (1992), S. 227-243 
    ISSN: 0894-3370
    Keywords: Engineering ; Electrical and Electronics Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Electrical Engineering, Measurement and Control Technology
    Notes: Purpose of this work is to present a new macromodelling approach for the simulation at the device level of large MOS integrated circuits, requiring only marginal modifications to be implemented in the widely used circuit simulator SPICE. This method results in a substantial saving in computing time and guarantees the same accuracy of SPICE. A prototype simulator based on this method has been developed and used to analyse several significant circuits. In addition, since the method is particularly suitable to be implemented in parallel computers, some results obtained with the CRAY-YMP/432 computer are provided.
    Additional Material: 16 Ill.
    Type of Medium: Electronic Resource
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  • 15
    Electronic Resource
    Electronic Resource
    Chichester [u.a.] : Wiley-Blackwell
    International Journal of Numerical Modelling: Electronic Networks, Devices and Fields 5 (1992), S. 23-39 
    ISSN: 0894-3370
    Keywords: Engineering ; Electrical and Electronics Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Electrical Engineering, Measurement and Control Technology
    Notes: An efficient algorithm is presented for the self-consistent numerical solution of the single-band effective mass equation. This algorithm has a different form depending on whether the effective mass is modelled as continuous or piecewise continuous. Coupled with a Poisson solver, an established algorithm is applied for the attainment of self-consistency. The rate of convergence to a self-consistent solution is investigated, and the solvers are applied to three different structures to demonstrate its versatility and robustness. The first of these is a nominally undoped quantum well AlGaAs/GaAs heterostructure, the second a doubly δ-doped GaAs homostructure and lastly a quasi-square well modulation-doped field effect transistor. The algorithm is of sufficient efficiency so as to allow the software to run reasonably quickly on a modern microcomputer.
    Additional Material: 12 Ill.
    Type of Medium: Electronic Resource
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  • 16
    Electronic Resource
    Electronic Resource
    Chichester [u.a.] : Wiley-Blackwell
    International Journal of Numerical Modelling: Electronic Networks, Devices and Fields 5 (1992) 
    ISSN: 0894-3370
    Keywords: Engineering ; Electrical and Electronics Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Electrical Engineering, Measurement and Control Technology
    Type of Medium: Electronic Resource
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  • 17
    Electronic Resource
    Electronic Resource
    Chichester [u.a.] : Wiley-Blackwell
    International Journal of Numerical Modelling: Electronic Networks, Devices and Fields 5 (1992) 
    ISSN: 0894-3370
    Keywords: Engineering ; Electrical and Electronics Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Electrical Engineering, Measurement and Control Technology
    Type of Medium: Electronic Resource
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  • 18
    Electronic Resource
    Electronic Resource
    Chichester [u.a.] : Wiley-Blackwell
    International Journal of Numerical Modelling: Electronic Networks, Devices and Fields 5 (1992), S. 53-66 
    ISSN: 0894-3370
    Keywords: Engineering ; Electrical and Electronics Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Electrical Engineering, Measurement and Control Technology
    Notes: This paper reviews the state of the art in hydrodynamic simulation of hot-carrier transport in semiconductor devices with application to MOSFET substrate current calculation. Hydrodynamic equations for semiconductors and derived and discretized expressions of these equations for device simulation are presented. Special attention has been given to the discretization of the input power term that appears in the energy conservation equation. A new discretization method for the input power term, based on power generation consideration, is proposed. Energy-based physical models for mobility and impact ionization are described for use in hydrodynamic simulation. Simulation results for both conventional and lightly-doped-drain MOSFETs are presented.
    Additional Material: 13 Ill.
    Type of Medium: Electronic Resource
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  • 19
    Electronic Resource
    Electronic Resource
    Chichester [u.a.] : Wiley-Blackwell
    International Journal of Numerical Modelling: Electronic Networks, Devices and Fields 5 (1992), S. 67-81 
    ISSN: 0894-3370
    Keywords: Engineering ; Electrical and Electronics Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Electrical Engineering, Measurement and Control Technology
    Notes: A novel spectral procedure for the numerical solution of non-linear boundary value problems is presented. The discrete spectral equations are solved by an iterative algorithm using space-domain preconditioning. The preconditioning operator is obtained by spatial weighting (or windowing) of the exact differential operator.Convergence behaviour of the iterative solution is investigated using an eigenvalue analysis. Theoretical estimates for the convergence rate and accuracy are compared with that achieved in a numerical application - a non-linear boundary value problem from semiconductor device modelling.The method combines the infinite-order exponential accuracy of spectral discretizations with the sparse structure of finite difference equations. This offers numerical advantages in comparison to previously developed Fourier-Galerkin algorithms, particularly important for physically ill-conditioned and strongly non-linear problems. The tradeoff of achievable accuracy versus computer time is easily controlled, thus making essential speed-ups possible for moderate accuracy requirements.
    Additional Material: 12 Ill.
    Type of Medium: Electronic Resource
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  • 20
    Electronic Resource
    Electronic Resource
    Chichester [u.a.] : Wiley-Blackwell
    International Journal of Numerical Modelling: Electronic Networks, Devices and Fields 5 (1992), S. 93-110 
    ISSN: 0894-3370
    Keywords: Engineering ; Electrical and Electronics Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Electrical Engineering, Measurement and Control Technology
    Notes: In this paper the application of the TLM method to electromagnetic scattering problems is investigated. To achieve the full computational benefits of using a time-domain numerical method, pulse excitation can be applied together with Fourier transformation of an output impulse response to yield frequency-domain results over a wide bandwidth. The configuration of the mesh is the same as that used in FD-TD scattering simulations (i.e., separation of the simulation space into total and scattered field regions). To terminate the exterior boundaries of the mesh, absorbing boundary conditions are applied to absorb the outward travelling waves. The effect of the absorbing boundaries on both time- and frequency-domain results is investigated. Frequency-domain scattered far-field patterns are presented for perfectly conducting square and circular cylinders illuminated by an incident plane wave (TM case). Forward and back scattering cross-section results obtained from a single TLM simulation indicate both the accuracy and efficiency of the method for calculating frequency-domain results over a wide bandwidth.
    Additional Material: 13 Ill.
    Type of Medium: Electronic Resource
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  • 21
    Electronic Resource
    Electronic Resource
    Chichester [u.a.] : Wiley-Blackwell
    International Journal of Numerical Modelling: Electronic Networks, Devices and Fields 5 (1992), S. 129-137 
    ISSN: 0894-3370
    Keywords: Engineering ; Electrical and Electronics Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Electrical Engineering, Measurement and Control Technology
    Notes: This paper reports the results of a study of an error parameter, m, which has been proposed as a measure for determining the effects on accuracy of the basic assumptions upon which TLM modelling of diffusion and heat flow has been founded. The nature of the m parameter is studied in detail by using a two-dimensional thermal diffusion problem. The use of m in the implementation of automatic timestepping is discussed in a practical three-dimensional engineering problem.
    Additional Material: 7 Ill.
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  • 22
    Electronic Resource
    Electronic Resource
    Chichester [u.a.] : Wiley-Blackwell
    International Journal of Numerical Modelling: Electronic Networks, Devices and Fields 5 (1992) 
    ISSN: 0894-3370
    Keywords: Engineering ; Electrical and Electronics Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Electrical Engineering, Measurement and Control Technology
    Type of Medium: Electronic Resource
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  • 23
    Electronic Resource
    Electronic Resource
    Chichester [u.a.] : Wiley-Blackwell
    International Journal of Numerical Modelling: Electronic Networks, Devices and Fields 5 (1992), S. 141-141 
    ISSN: 0894-3370
    Keywords: Engineering ; Electrical and Electronics Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Electrical Engineering, Measurement and Control Technology
    Type of Medium: Electronic Resource
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  • 24
    Electronic Resource
    Electronic Resource
    Chichester [u.a.] : Wiley-Blackwell
    International Journal of Numerical Modelling: Electronic Networks, Devices and Fields 5 (1992), S. 145-147 
    ISSN: 0894-3370
    Keywords: Engineering ; Electrical and Electronics Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Electrical Engineering, Measurement and Control Technology
    Type of Medium: Electronic Resource
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  • 25
    Electronic Resource
    Electronic Resource
    Chichester [u.a.] : Wiley-Blackwell
    International Journal of Numerical Modelling: Electronic Networks, Devices and Fields 5 (1992), S. 219-225 
    ISSN: 0894-3370
    Keywords: Engineering ; Electrical and Electronics Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Electrical Engineering, Measurement and Control Technology
    Notes: The paper provides an extension to the one-dimensional TLM diffusion model. The extended diffusion node presented here models the exact transport equation with diffusion drift and recombination of charge carriers in semiconductors. A general algorithm for providing a numerical solution to the transport phenomena is also presented here. The analytical solution for infinitely long semiconductors is compared with the TLM numerical results.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
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  • 26
    Electronic Resource
    Electronic Resource
    Chichester [u.a.] : Wiley-Blackwell
    International Journal of Numerical Modelling: Electronic Networks, Devices and Fields 5 (1992), S. 245-250 
    ISSN: 0894-3370
    Keywords: Engineering ; Electrical and Electronics Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Electrical Engineering, Measurement and Control Technology
    Notes: In order to efficiently store the information of a special class of matrices, a very useful algorithm has been derived and applied to the subsectional basis function approach to the method of moments. The algorithm represents a simple law of mapping and allows a reduction in the required computational storage by several orders of magnitude.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
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  • 27
    Electronic Resource
    Electronic Resource
    Chichester [u.a.] : Wiley-Blackwell
    International Journal of Numerical Modelling: Electronic Networks, Devices and Fields 5 (1992), S. 259-274 
    ISSN: 0894-3370
    Keywords: Engineering ; Electrical and Electronics Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Electrical Engineering, Measurement and Control Technology
    Notes: Three numerical methods are applied to the analysis of a rectangular waveguide-fed aperture radiating into a lossy media. A novel approach, the finite element method with an impedance boundary condition, and two established methods, the moment method and the mode-matching method, are presented. The methods are compared with respect to accuracy, execution time, memory requirement, and versatility. Four aperture geometries are chosen for detailed study: the full aperture of the rectangular waveguide, and three reduced apertures. The reflection coefficient of the aperture in contact with five known dielectrics is calculated in the frequency range 8·5-11·5 GHz. The theoretical results are validated by measurements performed on an HP8510 network analyser.
    Additional Material: 11 Ill.
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  • 28
    Electronic Resource
    Electronic Resource
    Chichester [u.a.] : Wiley-Blackwell
    International Journal of Numerical Modelling: Electronic Networks, Devices and Fields 5 (1992), S. 289-295 
    ISSN: 0894-3370
    Keywords: Engineering ; Electrical and Electronics Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Electrical Engineering, Measurement and Control Technology
    Notes: This paper describes an application of transmission-line modelling (TLM) for the solution of heat diffusion in a three-dimensional metallic structure, surrounded by a dielectric material. The example of heat propagation along an electric fuse embedded in granular silica is presented. Heat is generated by the flow of an electric current through the metallic element and results are shown for the variation of temperature with time and temperature distribution along the fuse element.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
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  • 29
    Electronic Resource
    Electronic Resource
    Chichester [u.a.] : Wiley-Blackwell
    International Journal of Numerical Modelling: Electronic Networks, Devices and Fields 5 (1992), S. 11-21 
    ISSN: 0894-3370
    Keywords: Engineering ; Electrical and Electronics Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Electrical Engineering, Measurement and Control Technology
    Notes: A novel algorithm has been implemented within our new semiconductor device simulation program TESSA that allows large signal periodic time-domain simulation to be performed by integrating over just one period of the excitation. Conventionally the need to integrate out initial transients, over many cycles, had effectively made such simulations impracticable. The algorithm can also be implemented in the field of circuit simulation so a combined large signal circuit/device simulation package is now a practical possibility.
    Additional Material: 10 Ill.
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  • 30
    Electronic Resource
    Electronic Resource
    Chichester [u.a.] : Wiley-Blackwell
    International Journal of Numerical Modelling: Electronic Networks, Devices and Fields 5 (1992), S. 41-52 
    ISSN: 0894-3370
    Keywords: Engineering ; Electrical and Electronics Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Electrical Engineering, Measurement and Control Technology
    Notes: A numerical time-domain modelling of non-linear microwave circuits is presented. It is based on a numerical procedure allowing the solution of the integro-differential equation driving the instantaneous electrical behaviour of a lumped-element circuit while accounting for the semiconductor device by means of an accurate numerical macroscopic model. This modelling is firstly validated by studying the DC turn-on and DC forward-reverse commutation of a PIN diode. The diode voltage and current waveform are qualitatively consistent with experimental ones, Moreover, the predicted recovery time values are found to be in good agreement with those issued from the classical analytical theory. Secondly, in order to illustrate the present capabilities of the model, the whole transient response of a back-to-back silicon PIN diode passive power limiter to a high-input-RF-power pulse is described. It is demonstrated that in the present case of a 2 μm-long PIN diode, the high-input-power steady-state operation only relies on one diode. To our knowledge, it is the first time this kind of simulation is applied to a two-diode circuit.
    Additional Material: 8 Ill.
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  • 31
    Electronic Resource
    Electronic Resource
    Chichester [u.a.] : Wiley-Blackwell
    International Journal of Numerical Modelling: Electronic Networks, Devices and Fields 5 (1992), S. 1-1 
    ISSN: 0894-3370
    Keywords: Engineering ; Electrical and Electronics Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Electrical Engineering, Measurement and Control Technology
    Type of Medium: Electronic Resource
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  • 32
    Electronic Resource
    Electronic Resource
    Chichester [u.a.] : Wiley-Blackwell
    International Journal of Numerical Modelling: Electronic Networks, Devices and Fields 5 (1992), S. 3-9 
    ISSN: 0894-3370
    Keywords: Engineering ; Electrical and Electronics Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Electrical Engineering, Measurement and Control Technology
    Notes: A detailed one-dimensional energy transport model for unipolar GaAs/AlGaAs heterojunction structures is implemented, by extending the basic transport equations to include the energy balance equation for electrons. A non-uniform grid-mesh is used to obtain short simulation times, while the grid-distance at the N-n++ interface is small, which is essential to obtain a low reverse current.
    Additional Material: 3 Ill.
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  • 33
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 43 (1992), S. 147-158 
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A review of our own work on ab initio calculation of nonlinear optical properties by the finite oligomer method is presented. Various computational considerations such as geometry determination and choice of basis set are discussed as well as extrapolation to the long-chain limit. For cases where the extrapolation is problematic, two potential solutions are suggested. We also analyze several important areas ripe for investigation including the frequency-dependence, the effect of vibrational distortion, and the role of electron correlation.
    Additional Material: 3 Ill.
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  • 34
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 43 (1992), S. 573-578 
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: For the CF4+, PF5+, SF6+, and MoF6+ ions appearing after the F1s photoionization, the possibility of dissociation has been shown by the ab initio MO LCAO method within the Z + 1 core equivalent model. According to the calculations, the decay channel AFn+ → AFn-1+ + F(1s12p6) is energetically open for the ions. So the interpretation of the gas-phase emission FKα spectra, in which the bands are assigned to the discrete transition energies, can be unacceptable for these ions. The conditions and signs of such failure are discussed.
    Additional Material: 1 Ill.
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  • 35
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    International Journal of Quantum Chemistry 44 (1992), S. 67-80 
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The intramolecular (internal) charge sensitivity analysis (ICSA) is presented in the molecular orbital (MO) resolution, with diagonal idempotency constraints being imposed on the MO occupations, n, which can then be considered as independent electron population variables of the system for the assumed fixed shapes of MOS. The standard closed-shell (C.S.) SCF MO framework is adopted with the energy function E(n) approximated by the average energy of a configuration expression to cover fractional MO occupations. The components of the gradient of the auxiliary energy function, including the constraint terms, with respect to n, identified as negative MO internal electron potentials, vanish identically for the ground-state c.s. configuration, whereas their responses to hypothetical intramolecular charge displacements assure the system stability. An application of the ICSA to the iterative SCF procedure is suggested. Illustrative results for the water molecule are reported and general properties of molecular normal orbitals (eigenvectors of the hardness matrix) are discussed. © 1992 John Wiley & Sons, Inc.
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  • 36
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    International Journal of Quantum Chemistry 44 (1992), S. 97-111 
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
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  • 37
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    International Journal of Quantum Chemistry 44 (1992), S. 327-336 
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Ab initio self-consistent field (SCF) molecular orbital calculations were carried out at the MP2/431G* level to determine the effect of substituent groups, —F, —NH2, —OH, —CH3, CH2=CH—, and H—C≡C - on the C≡P triple bond. Although there are considerable differences between the electronegativities of these substituent groups, a characteristic feature found in phospha alkyne derivatives is the weak sensitivity of the C≡P bond length to the substituent at the carbon atom. The molecular electrostatic potential analysis clearly reflects the strength of the electronegativity of these substituent groups and their ability to attract the polarizable charge from the C≡P triple bond. MEP analyzes further indicates that these derivatives of phospha alkynes are most likely to attract incoming electrophiles to the π-electron region of the C≡triple bond. Transition metals are coordinated “sideways” with phospha alkynes, and in this configuration, the lone-pair electrons of the phosphorus atom are unlikely to interact with the metal. © 1992 John Wiley & Sons, Inc.
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  • 38
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    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: This work examines the possibility of finding an electron-hole and an electron-pair simultaneously in a π-system substituted by an electron-donating (NH2) and/or electron-withdrawing (NO2) group. The contributions of various ionic [(+), ( ↑ ↓ )] structures are calculated from ab initio SCF-CI wave functions, using a recently developed general multielectron population analysis. The molecules studied are two monosubstituted ethylenes, aminoethylene and nitroethylene, and a disubstituted ethylene, the 2-nitroethenamine (push-pull ethylene) in its two configurational forms. The influence of the NH2 and/or NO2 group in delocalization and ionic (vs. covalent) character of the C=C double bond are investigated, along with examining the experimental chemist formalism of electron-pair “displacements” in several resonance structures. Analysis of mutual dependence of an electron-hole and an electron-pair, at short and long distances, leads to the conclusion that a push-pull π-system can stimulate the simultaneous existence of an electronhole and an electron-pair even for nonvicinal positions. The relationship between the electronpair distributions and contributions of the corresponding structures are also examined; the effects of electronic correlation are analyzed as well. © 1992 John Wiley & Sons, Inc.
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  • 39
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    International Journal of Quantum Chemistry 44 (1992), S. 319-331 
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: We explore a hybrid methodology in which the Hartree-Fock energy and density are combined with the nonlocal exchange functional of Becke (1988) and the nonlocal correlation functional of Lee, Yang and Parr (1988) to yield an estimate of the Schrödinger total energy. The resulting mean absolute deviation from a large number of experimental atomization energies, ionization potentials, electron affinities, and proton affinities is 3.86 kcal/mol. Performance comparisons are made with the recently developed G2 theory and nonconventional interpretations of the density functionals are discussed. © 1992 John Wiley & Sons, Inc.
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  • 40
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    International Journal of Quantum Chemistry 44 (1992), S. 311-318 
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: We use the continuous formulation for the matrix Hartree-Fock method, called the generator-coordinate-Hartree-Fock method, to rephrase a theorem of Nakatsuji et al. concerning the improvement of the Hellmann-Feynman forces calculated with nuclei-centered GTO basis functions. We show that we do not need to increase the size of the basis set in order to obtain reliable Hellmann-Feynman forces, but just use a self-consistent set so that, starting with some s-type GTOS, the p-type GTOS are a subset of the derivatives of those s-type GTOS, and so on. We illustrate this feature in calculations on small dyatomic molecules. © 1992 John Wiley & Sons, Inc.
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  • 41
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    International Journal of Quantum Chemistry 44 (1992), S. 673-686 
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: We report on the progress in a study to determine the structure of radiation-induced Mn defect complexes in CaF2. The purpose of this study is to correlate the calculated transition energies with those measured experimentally and to determine what effect the inclusion of the external lattice field has on these transitions. Unrestricted open shell Hartree-Fock Self-Consistent Field (UHF) calculations were performed on the unperturbed F-center [Ca4F6Vac]1+ S = 1/2, the unperturbed Mn2+ center [MnF8]6- S = 5/2, S = 3/2 and the Mn2+ perturbed F-center [Mn2Ca2F6Vac]1+ S = 11/2, S = 9/2 defect clusters. A method by which the effects of the external lattice field may be incorporated in the SCF procedure is developed and used in these calculations. Several transition energies are calculated and Mulliken population results for these clusters are presented and discussed. © 1992 John Wiley & Sons, Inc.
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  • 42
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    International Journal of Quantum Chemistry 44 (1992), S. 687-701 
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: We report on the results of electronic band structure calculations of bulk ZnSe, bulk ZnS, and the (ZnSe)1(ZnS)1 strained-layer superlattice (SLS) using the ab initio factorized linear combination of atomic orbitals method. The bulk calculations were done using the standard primitive nonrectangular 2-atom zincblende unit cell, while the SLS calculation was done using a primitive tetragonal 4-atom unit cell modeled from the CuAu I structure. The analytic fit to the SLS crystalline potential was determined by using the nonlinear coefficients from the bulk fits. The CPU time saved by factorizing the energy matrix integrals and using a rectangular unit cell is discussed. © 1992 John Wiley & Sons, Inc.
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  • 43
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    International Journal of Quantum Chemistry 44 (1992), S. 717-724 
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The conventional use of pure angular momentum state representations in the algorithms for reactive scattering is discussed and the merits of alternative formulations in a finite element framework are considered with respect to possible numerical effectiveness. Four- and seven-dimensional hyperspheres are discretized as means of describing three- and six-dimensional scattering problems. © 1992 John Wiley & Sons, Inc.
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  • 44
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    International Journal of Quantum Chemistry 44 (1992), S. 751-760 
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: External field effects are introduced in both charge and orbital control terms of Klopman-Salem formalism for the study of chemical reactivity in condensed phase. An analytical expression is derived for the change of the interaction energy between a nucleophile and an electrophile from gas to solution phase. The resulting simple expression contains the effect of the external field, in terms of the variation of the electrophilic superdelocalizability index associated with the highest occupied molecular orbital (HOMO) of the nucleophile. Two classical reactions are analyzed to illustrate the usefulness and reliability of the proposed formalism. © 1992 John Wiley & Sons, Inc.
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  • 45
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    International Journal of Quantum Chemistry 44 (1992), S. 761-771 
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: In this article we generalize the necessary conditions for a topological definition of the concept of molecular structure, showing that it may be independent of the particular criterion chosen, as long as it fulfills some general conditions and may give rise to the concept of a category of stable chemical structures. We proceed to introduce a local metric in the objects of this category by using the properties of metric space bundles, and this allows us to propose a general system of reaction mechanisms within this framework of the theory of categories. We conclude by proposing a single diagram that encompasses the whole theory of stable structures and reaction mechanisms. © 1992 John Wiley & Sons, Inc.
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  • 46
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    International Journal of Quantum Chemistry 44 (1992), S. 657-665 
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: An example of an isolated resonance with highly non-Lorentzian line-shape has been found for the gas-surface diffraction system He(21 meV)/Cu(115 ). When the corrugation strength parameter for the surface is very slightly varied, the signature of the narrow resonance structure shifts. © 1992 John Wiley & Sons, Inc.
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  • 47
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    International Journal of Quantum Chemistry 44 (1992), S. 667-672 
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The electronic and structural properties of the single N and the pair N2 complex substitutional impurity systems in type-IV semiconductors (C, Si, and Ge) are investigated through an ab initio LCAO cluster model. We find that the stable position for N atoms (N and N2) is off center with dislocation in a 〈111〉 direction to form sp2 bonds with the host atoms. Particularly for ionized complex N2+ there is a symmetry break lowering the point group symmetry of the system from D3d to C3v. We present also the results for hyperfine interactions over the impurity and its nearest neighbor which for isotropic terms are in fair agreement with the experiment. © 1992 John Wiley & Sons, Inc.
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  • 48
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    International Journal of Quantum Chemistry 44 (1992), S. 703-716 
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: We report on the results of calculations of the electronic structure of α-quartz that were made using the first principles, factorized linear combination of atomic orbitals method. Results were obtained for the primitive 9-atom, and orthorhombic 18- and 72-atom unit cells. Application of this method to the calculation of the electronic structure of the neutral oxygen vacancy in α-quartz is discussed and results obtained using a 72-atom unit cell are given. © 1992 John Wiley & Sons, Inc.
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  • 49
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    International Journal of Quantum Chemistry 44 (1992), S. 737-749 
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: In the present study we introduce a time-dependent wave packet method to treat electronically non-adiabatic processes explicitly in the coupled adiabatic state representation. The method is applied to the predissociation of the MgCl (A2II) state and is shown to be easy to implement, with the computational effort being comparable to the corresponding calculation in the diabatic basis. © 1992 John Wiley & Sons, Inc.
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  • 50
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    International Journal of Quantum Chemistry 44 (1992), S. 725-736 
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Surface-molecule interactions and reactions are important elementary steps of catalytic reactions. Since they involve interactions between infinite and finite systems, modelings are necessary for theoretical investigations of catalytic reactions on a surface. The cluster model (CM) is most frequently used for quantum chemical calculations but neglects the effect of the bulk solid. For including such effect, ( 1 ) embedding the cluster onto a surface (actually into a larger cluster) is a method proposed by Grimley and Pisani, and (2) dipping the adcluster (admolecule + cluster) onto the electron bath of the solid and letting the system be at equilibrium for electron and spin exchanges is another model proposed by Nakatsuji. We show some applications of the embedding cluster model (ECM) and the dipped adcluster model (DAM). We will also report in the lecture on the study of the photochemical decomposition reaction of MnO4- into MnO2- + O2. © 1992 John Wiley & Sons, Inc.
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  • 51
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    International Journal of Quantum Chemistry 44 (1992), S. 879-894 
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ACES II, a new program system for ab initio electronic structure calculations is described. The strengths of ACES II involve the use of many-body perturbation theory (MBPT) and coupled-cluster (CC) theory for calculating the energy, geometry, spectra, and properties of small- to medium-sized molecules. This paper gives a brief overview of the ACES II project, describes many features of the program system, and documents a number of benchmark calculations. © 1992 John Wiley & Sons, Inc.
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  • 52
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    International Journal of Quantum Chemistry 44 (1992), S. 807-815 
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Solvation effect on the tunneling rates in the case of coupled motion of two protons along the reaction coordinate was semiempirically, CNDO/2, computed. The following molecular transition-state complexes (TSC) were studied: +AH - BH - A, where A was either NH3 or H2O and BH was HF. Solvation was modeled with water molecules attached to each side of the perpendicular axis, through the bridge HF at different distances F/O. FN and FO (on-line) distances were also varied. Lower and narrower barriers were observed with the close positioning of the solvating molecules. This effect is reflected in higher tunneling probabilities. Thus, solvation favors the tunnel phenomenon in proton-transfer processes. © 1992 John Wiley & Sons, Inc.
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  • 53
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    International Journal of Quantum Chemistry 44 (1992), S. 793-806 
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: An ab initio analysis of the reaction of molecular hydrogen with the Zr-imido complex (NH2)2Zr= NH is reported. Several interesting points are noted. The calculated stretching frequency of the Zr=N bond in (NH2)2Zr=NH is 860 cm-1 when properly scaled to account for electron correlation effects. The value supports the assignment of an infrared (IR) band at 865 cm-1 to the Zr=N stretch of a tetrahydrofuran (THF) adduct of the putative reactive intermediate (NHSi′)2Zr=NSi′. Although a weakly bound, H2 complex is found, the interaction is small (1.3 kcal mol-1) compared with experimentally characterized H2 complexes. Variations in bond lengths and intrinsic stretching frequencies demonstrate that π-bonding for amido (NH2) ligands can be substantial in a coordinatively saturated complex. H2 activation by the bis(amido)imido reactive intermediate is calculated to be significantly more favorable by the 1,2-addition of H2 across the Zr=N bond to form the tris(amido)hydride than a sigma-bond metathesis pathway. The transition state (TS) for the addition of H2 across the Zr=N bond of the bis(amido )imido complex is 9.8 kcal mol-1 above the charge transfer (CT) complex, (NH2)2Zr=NH = H2 at the MP2 level; the reverse process, extrusion of H2 from the tris(amido)hydride has a 28.2 kcal mol-1 barrier. The geometry of the four-center TS is of interest, deviating markedly from that of a square and being more “kite” shaped (i.e., one obtuse and three acute angles). Mulliken Bond Overlap Populations suggest that there is some interaction between the Zr and the H atom being transferred (Hl) in the various TSs studied. It is suggested that the interaction plays an important role in the ability of the Zrimido complexes, and indeed other high-valent, multiply bonded complexes, to activate X=H (X=H, C, Si, N, and H) bonds. The design of materials and catalysis precursors which enhance the metalhydrogen interaction in the TS could conceivably lead to lower chemical vapor deposition (CVD) processing temperatures and higher catalytic activities. © 1992 John Wiley & Sons, Inc.
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  • 54
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    International Journal of Quantum Chemistry 44 (1992), S. 837-852 
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The implementation of the density-functional scheme requires the knowledge of the exchange and correlation potential, Vxc, as a functional of the electron density. In the local-density approximation (LDA) this potential becomes a function of the local value of the density. This ansatz breaks down qualitatively at a surface because of its neglect of long-range electron-electron correlations in the presence of strong charge inhomogeneity. This breakdown is of relevance in the context of various surface spectroscopies. We outline a scheme for going beyond the LDA without invoking gradient expansions. This scheme is based on establishing an interrelation between density-functional theory and many-body perturbation theory. In this scheme Vxc is obtainable from the knowledge of the electron self-energy Σxc. We solve an exact integral equation relating these two quantities for the electron-gas surface with use of the GW approximation for the self-energy. We establish a “nonlocal” relation between Vxc and the electron density which allows us to carry out nonlocal density-functional calculations with the same ease as LDA-based calculations. We present results of the first application of our method for the case of Al and Pd surfaces. In addition, we report on work in progress devoted to a detailed comparison of the density-functional and quasiparticle pictures of electronic excitations at a metal surface. © 1992 John Wiley & Sons, Inc.
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  • 55
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    International Journal of Quantum Chemistry 44 (1992), S. 377-391 
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: After a brief discussion of the deformation of the ground-state electron density asymptotically, in free space homonuclear diatomics by dispersion interactions, dimers in dense homogeneous plasma will be treated. Polarization interaction will be shown to lead to an R-4 interaction energy at large internuclear separation, R, supplementing the well-known long-range oscillatory interaction. The relevance of these interactions, when suitably modified for a heterogeneous environment, to lateral forces between CO molecules chemisorbed on a transition metal surface will then be considered, with specific reference to experiments on thermal desorption. Finally, the theory of the inhomogeneous electron liquid in intense magnetic fields will be briefly discussed, for both localized and delocalized electrons. © 1992 John Wiley & Sons, Inc.
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  • 56
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    International Journal of Quantum Chemistry 44 (1992), S. 443-453 
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The He I and He II photoelectron (PE) spectra of methyl pseudohalides (MeNCO, MeNCS, MeNCSe, MeSCN, and MeSeCN) have been recorded. Assignments are based on ab initio quantum chemical calculations, and their comparison with high-resolution He I spectra and He I/He II band intensity ratios. Contradictions found in previous works are largely resolved. The strikingly different spectra of the isomeric forms are interpreted using a consistent model for a methyl-distorted NCX substructure. The effects of the heavy atoms are also discussed. © 1992 John Wiley & Sons, Inc.
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  • 57
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    International Journal of Quantum Chemistry 44 (1992), S. 487-495 
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Elements of the frequency-dependent polarizability tensor are obtained from the quadratic response function (QRF). This is accomplished from equations of motion (EOM) which relate QRFS and the linear response function (LRF). The response functions are evaluated within the random-phase approximation (RPA), where the EOM are exact in a complete basis. Hence, the agreement between LRF and QRF polarizability provides a criterion for basis set selection when calculating second- as well as third-order properties. Numerical examples are provided for the static and dynamic polarizability of H2O. © 1992 John Wiley & Sons, Inc.
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  • 58
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    International Journal of Quantum Chemistry 44 (1992), S. 505-515 
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The potential energy surface of glycolic acid was investigated using ab-initio 4-31G SCF calculations. Geometries, energies, and wavenumbers for all seven symmetry-unique local minima are reported together with all reaction paths and their energetical barriers. © 1992 John Wiley & Sons, Inc.
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  • 59
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    International Journal of Quantum Chemistry 44 (1992), S. 543-550 
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Calculations of electronic structure and bonding via the SCMEH-MO method with limited Cu 3d, 4s, and 4p configuration interaction, have been carried out on the tetragonally coordinated (D2h symmetry) CuCl6(NH4)4 structural cluster unit in crystalline (NH4)2CuCl4. The results are compared with those of other calculations. The calculated electronic spectrum, electric field gradient (EFG), and magnetic data are compared with experiment. © 1992 John Wiley & Sons, Inc.
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  • 60
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    International Journal of Quantum Chemistry 44 (1992), S. 563-573 
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Gas phase acrylonitrile electron affinity has recently been estimated to be in the range 0.01 to 0.02 eV. In spite of a strong theoretical prediction on the existence of stable anions for molecules having dipole moments larger than the critical 1.625 D, it has not been possible to obtain a positive electron affinity for acrylonitrile (dipole moment = 3.9 D) by ab initio SCF and MP2 calculations using 6-31G, 6-3IG*, 6-31+G(d), 6-31++G(d, p), and 6-311++G(2d,2p) bases. © 1992 John Wiley & Sons, Inc.
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    International Journal of Quantum Chemistry 44 (1992), S. 575-585 
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The stability of different conformational isomers of partially deuterated radical cations of ethane, butane, and cyclopropane is studied at the HF/6-31G** and MP2/6-31G** levels. It is shown that the superposition patterns of spectra corresponding to different isomers, observed in ESR spectroscopy, are accurately reproduced by Boltzmann statistics based on differences in vibrational zero-point energies (ZPE), provided that the temperature is high enough to overcome existing barriers toward internal pseu-dorotation in the cations. For the ethane and butane cations, the most stable conformations are, as expected, those which are deuterated in the short CH bonds, while this is found not to be the case for the cyclopropane cation. The latter result is explained by shifts in the low-frequency bending modes, which counteract the anticipated isotope effect on the C—H stretching modes. © 1992 John Wiley & Sons, Inc.
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  • 62
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    International Journal of Quantum Chemistry 44 (1992), S. 153-160 
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: In this work use is made of algebraic techniques developed for the evaluation of Vibration-Translation energy transfer in atom-diatom collisions to obtain the energy eigenvalues of the one-dimensional quartic oscillator. We have found that even our zero order approximation results are very close to the exact ones and when second-order perturbation theory is used, they improve even for high values of the anharmonicity parameter. © 1992 John Wiley & Sons, Inc.
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  • 63
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    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: TheMoenergy level patterns of molecules deduced directly from the pictures of molecules (VIF method) are shown to implicitly include the overlap integrals between highly nonorthogonal AO's and to be invariant under crucial nonunitary transformations. Further, machine-computed MO levels are found to readily yield chemically interpretable information such as the nonbonding MO levels and the nature of the HOMO and LUMO once the proper invariant quantity found here is subtracted out from the numerical energies. The resulting EHT, Gaussian STO-3G, … type computed MO energy level patterns then show correspondence with the VIF-pictorially deduced level patterns obtained without point group symmetries. © 1992 John Wiley & Sons, Inc.
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  • 64
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    International Journal of Quantum Chemistry 43 (1992), S. 119-134 
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A new formalism and algorithm is developed for solving the general-order time-dependent Hartree-Fock (TDHF) problem. It is shown that for any order a generalization of the TDHF equations can be derived where all lower-order solutions constitute a constant term. This makes it very easy to obtain high-order solutions. As the space required for the mapping of density matrices to Fock matrices in a problem of a giver order is largely reduced, we can perform the most time-consuming steps within the core memory of the machine and easily manipulate vector products via optimum routines. The second hyperpolarizability γ is obtained from the secondorder TDHF solution via a 2n rule. The formalism also allows for expressing all terms in the equation diagrammatically, which provides additional physical insight and a more systematic evaluation of terms. To illustrate the method, TDHF results are presented for trans-butadiene and carbon monoxide for several optical processes, including correlation corrections to their static hyperpolarizabilities obtained via coupled cluster (CCSD) and many-body perturbation theory. The hybrid TDHF/CCSD method provides excellent agreement with the DC-SHG experiments (χ||(2) = 11.4 x 10-32 esu/mol compared to 12.9 ± 11.4 × 10-32 esu/mol and χ||(3) = 149 compared to 144 ± 4 × 10-39 esu/mol).
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  • 65
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    International Journal of Quantum Chemistry 43 (1992), S. 135-146 
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Ab initio and model calculations on linear clusters of acetylene molecules have been carried out to identify the effect of weak intermolecular interaction on the intrinsic dipole polarizability (-) and the second hyperpolarizability (γ) and, in particular, to determine the three-body and higher-order effects. Ab initio and model calculations on a linear dimer show clearly that the evolution of properties from the separated limit is largely a consequence of the mutual polarization as the monomers begin to interact. This reveals that intermolecular quantum features are not significant. Furthermore, higher-order response properties play a negligible role in the evolution of lower-order cluster properties. For instance, the hyperpolarizability γ of the monomer is relatively unimportant in the evolution of α of the dimer; the change in α due to dimer formation is dictated largely by the mutual polarization via the intrinsic α′s of the monomer. With this determination, an electrical interaction model can be used to explore α and γ of long acetylene chains, and this serves as a guide to the vibronic coupling effects on hyperpolarizabilities of longchain species. We find, in particular, that the hyperpolarizability of the subunits of long acetylene chains are dramatically enhanced by intermolecular electrical interaction.
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  • 66
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    International Journal of Quantum Chemistry 43 (1992), S. 171-173 
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    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
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  • 67
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    International Journal of Quantum Chemistry 43 (1992) 
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    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
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  • 68
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    International Journal of Quantum Chemistry 43 (1992), S. 159-169 
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Components of the crystal quadratic susceptibility tensor χ(2) for second-harmonic generation are calculated for the title compound, 4-(N, N-dimethylamino)-2-acetamido-nitrobenzene. Input data are the crystal structure and refractive indices and CNDO hyperpolarizabilities; two different sets of refractive indices give similar results. The calculations yield effective polarizabilities as well as both rigorous and anisotropic Lorentz local electric fields. Susceptibility components are close to 10 pm V-1, rather smaller than those deduced experimentally and showing a weaker dependence on direction; Kleinman symmetry is mostly observed within 10%. Screened dipoledipole interactions using CNDO dipole moments amount to -80 kJ mol-1, implying permanent fields of 2 GV m-1.
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  • 69
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    International Journal of Quantum Chemistry 43 (1992), S. 175-195 
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The correlation between topological features of molecular structure and physicochemical as well as biological properties of molecules were examined for some sets of compounds, using graph-theoretical desciptions. It was found that the topological similarity plays a role in the determination of molecular properties for almost all compound sets studied. As a conclusion, one can presume that the less elaborated and complicated similarity measure based on the graphtheoretical description is sufficient in the case of distinct structure-property dependence.
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  • 70
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    International Journal of Quantum Chemistry 43 (1992), S. 209-214 
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: We generalize the usual complex virial theorem using a procedure of complex scaling for only some of the coordinates of the system. This result can also be considered as an extension of the virial theorem obtained in a previous work using real scaling for a subset of coordinates.
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  • 71
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    International Journal of Quantum Chemistry 43 (1992), S. 197-207 
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Attempts to calculate the metal-ring distance in the ferrocene molecule using a well-tried minimal basis reveal serious deficiencies in the minimal-basis SCF model of the electronic structure of organometallics. It is found that the lowest state of the molecule in this approximation is a triplet and that there is a whole manifold of “states” in the ground-state region that have broken spatial symmetry and high-spin multiplicity.
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  • 72
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    International Journal of Quantum Chemistry 43 (1992), S. 215-219 
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Ab initio MP2/4-31G** calculations indicate that the most stable form of C3NH is bent and singlet and that the linear structure corresponds to a maximum. The effect of changing the CNH angle on the total energy is slight, but it is quite pronounced on the molecular polarity. The wider angle tends to increase the polarity of C3NH. MP2/4-31G** calculations predict a difference of polarity between linear and bent structures of 0.8 D.
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  • 73
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    International Journal of Quantum Chemistry 43 (1992), S. 221-250 
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: It is shown that in the framework of coupled cluster theory both the correlation energy per unit cell and quasi-particle band structures of polymers can be computed directly from matrix elements of the excitation operator and the two-electron integrals calculated in localized orbital basis. Further, it is described how to thake advantage of the localized nature of the orbitals applied. Ab initio test calculations on a finite model system similar to the Pariser-Parr-Pople Hamiltonian are presented.
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  • 74
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    International Journal of Quantum Chemistry 43 (1992), S. 251-258 
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The variation-iteration method of Svartholm has been applied to the momentum-space Schrödinger equation for one-dimensional two-electron systems. The first and second iteration momentum-space wave functions have been evaluated in analytical forms. The momentum representation of the exact Hartree-Fock ground-state wave function is chosen as the initial function. The influence of electron correlation on the distribution of momentum-space probability density has been studied. It is shown for the one-dimensional McWeeny-Coulson problem that the numerical value of the ground-state energy of the one-dimensional two-electron atom is between the minimum energy values ε1/2 and ε1.
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  • 75
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    International Journal of Quantum Chemistry 43 (1992), S. 273-280 
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    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A new way of computing two-electron integrals over Slater functions by means of optimized Gaussian expansions is proposed. Expansions up to five terms have been optimized for 1s, 2s, and 2p STOs and applied to the computation of many-center two-electron integrals. All these integrals can be quickly evaluated and the SCF energy computed from them is very accurate.
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  • 76
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    International Journal of Quantum Chemistry 43 (1992), S. 259-272 
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The single-particle Green's function is used to generate a new zero-order Hamiltonian. The idea to generate a new zero order from the previous zero order by incorporating perturbative corrections up to certain order is attractive since it allows an iterative procedure to repeatedly improve the results by decreasing the perturbation. In particular, in those cases where the Hartree-Fock Hamiltonian is not a good approximation to the full Hamiltonian and where perturbation theory usually does not produce sufficiently accurate results, one might hope that such a repetitive procedure ultimately yields an improved zero order and accurate perturbative corrections from this newly generated zero order. Two such approaches are investigated: first, one in which the ω-independent part of the self-energy is fully incorporated in the zero order and, second, one in which the correlation energy is incorporated in a one-electron potential in an average way. Numerical calculations are reported.
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  • 77
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    International Journal of Quantum Chemistry 43 (1992), S. 311-312 
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
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  • 78
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    International Journal of Quantum Chemistry 43 (1992), S. 281-300 
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A simple valence-bond approach is considered for treating extended systems of equivalent atoms. In this approach, a limited nonorthogonal basis set of atomic orbitals is utilized and only nearest-neighbor interactions are supposed. By exploiting then the translational invariance of the system, expressions for the matrix elements between antisymmetrized products of such nonorthogonal orbitals are derived in an algebraic form suitable for the numerical implementation on a computer. The one-band linear case is explicitly considered. Some possible applications of the proposed approach and its connections with model Hamiltonians such as the Hubbard and the Heisemberg ones are also discussed.
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  • 79
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    International Journal of Quantum Chemistry 43 (1992) 
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    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
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  • 80
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    International Journal of Quantum Chemistry 43 (1992), S. 301-309 
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The ground states of atoms and molecules Li-, Be, LiH, LiH2-, and Li2 have been calculated using the n-electron wave functions built up with two kinds of geminals. As a comparison, the above systems have been calculated with the Hartree-Fock self-consistent field and the multi-configuration self-consistent field method as well. The results show that the wave functions in this work are capable of describing the electron correlations, and both kinds of geminals can be taken as a starting point in building up n-electron ground states.
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  • 81
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    International Journal of Quantum Chemistry 43 (1992), S. 313-320 
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    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: We propose a novel method for calculation of the electronic correlation energy of molecular systems in the path integral formalism. The procedure consists of saddle-point expansion of the path integral around the Hartree-Fock energy. By one loop-expansion of the molecular path integral into the generalized space phase of the molecular orbitals, the shift energy is obtained.
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  • 82
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    International Journal of Quantum Chemistry 43 (1992), S. 321-326 
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    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Ab initio Hartree-Fock crystal orbital results were used as input for the calculation of exciton energies in the Tamm-Dancoff and random-phase approximation for polymers with helical symmetry. The calculations were applied to a hydrogen fluoride chain. We show that the Tamm-Dancoff method is a good approximation to the random-phase theory. Furthermore, the influence of the band-band interaction in the exciton calculation has been investigated.
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  • 83
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    International Journal of Quantum Chemistry 43 (1992), S. 343-352 
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    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: In the present paper, the role of (n - 1)ƒ orbitals in metal-metal quadruple bonds was studied. It was shown by the calculations that the probabilities for finding the σ-, π-, and δ-electrons between two metal atoms, under the influence of the ƒ orbitals on the metal-metal quadruple bonds, increased while their mean kinetic energy components along the metal bond axis decreased. In addition, the effects of the ƒ orbitals upon the σ, π, and δ metal-metal bonds were different. In general, σ 〈 π 〈 δ.
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  • 84
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    International Journal of Quantum Chemistry 43 (1992), S. 327-342 
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    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The local origin/local orbital (LORG) method of Hansen and Bouman has been implemented with the intermediate neglect of differential overlap Hamiltonian for spectroscopy (INDO/S). The method is shown capable of demonstrating the inductive effects associated with electron-withdrawing substituents through the diamagnetic shielding term. In addition, the method is capable of differentiating chemical shift in differing bond environments. The calculated paramagnetic contribution, however, is deficient for substituents that saturate the minimal basis such as oxygen and fluorine, which severely limits the general utility of the procedure. Through the utilization of reduced linear equations for the paramagnetic term, the method is amenable to any molecule for which a self-consistent field can be performed and therefore can potentially be used to study very large systems. At present, however, the LORG method when used with the rapid INDO/S model Hamiltonian does not reliably reproduce the paramagnetic contribution to the shielding.
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  • 85
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    International Journal of Quantum Chemistry 43 (1992), S. 353-374 
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    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Following the recent developments of the charge sensitivity analysis (CSA) in the atoms-in-molecules (AIM) resolution, the corresponding CSA quantities in the orbital (or shell) resolution (OR) are defined. The OR electron population variables, in the ordinary closed-shell SCF problem, are the elements of the bond-order matrix P, and their conjugates, “chemical potentials,” FT = ∂E/∂P, are the respective Fock matrix elements, appropriate for the representation in question; here E is the SCF energy. The second derivatives ∂2E/∂P∂P define the OR hardness tensor from which all related OR CSs, e.g., the hardness, softnesses, Fukui function (FF) indices, etc., can be determined. The rigid potentials and hardness tensor, corresponding to the “frozen” orbital approximation, are examined in more detail, and the decoupled representation of the normal orbitals (NoO) is introduced, in which the rigid hardness tensor becomes diagonal. Illustrative valence-shell NoO contours for the water molecule are given and discussed. The new approximation for the OR FF indices, as the orbital occupation probabilities, is proposed on the basis of the density matrix functional development of Donnely and Parr for natural orbitals, and the relevant expressions for the molecular fragment (collection of orbitals) quantities are summarized.
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  • 86
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    International Journal of Quantum Chemistry 43 (1992), S. 375-392 
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    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Two numerical codes, a complex face vector F and a real face vector D are developed for the characterization of square-cell configurations (lattice animals), used for representing the shapes of molecular monolayers and cross sections of molecular surfaces. The real face vector D represents all the intrinsic properties, size, and shape of the lattice animal. The complex face vector F contains complete information about the size, the shape, and also the placement of the particular lattice animal with respect to the lattice. Based on the properties of the face vectors, a method is developed for the classification of similar animals into equivalence classes. The face vector method is proposed for an algorithmic, nonvisual computer analysis of similarity of shapes of molecular monolayers and planar domains of cross sections of molecular surfaces, approximated by lattice animals.
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  • 87
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    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The electron-vibrational problem of the general nonadiabatic molecular systems has been solved by means of the quasi-particle transformations. The SCF ab initio solution of the nonadiabatic fermion Hamiltonian yields stabilization of the electronic ground-state energy due to electron-phonon interaction and it also gives the corrections to the one- and two-particle terms. Two two-particle correction yields effective attractive electron-electron interaction, but in the form different from Frölich's effective electron-electron interaction term. In contrast to the standard electron-phonon Hamiltonian of solid-state physics that does not take into account the possible effects of nonadiabaticity of a system, the presented nonadiabatic theory yields also one-particle corrections. The presence of this term in the Hamiltonian might play a crucial role in the theory of superconductivity since the superconductors are nonadiabatic systems.
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  • 88
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    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: An exact solution for the electron-vibrational problem of the nonadiabatic molecular system has been obtained. By the quasi-particle transformation technique, the fermionic Hamiltonian has been derived and solved at the ab initio level. Results clearly and unambiguously show that the gap formation due to nonadiabatic electron-phonon coupling is mediated by the one-particle electron-phonon interaction term, whereas the two-particle one represents just a correction to the correlation energy. The temperature dependence of the gap and electronic specific heat connected with the electron-phonon coupling have also been derived.
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  • 89
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    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Conditions for low and high Tc superconductors following from the nonadiabatic electron-vibrational theory at ab initio level have been obtained. According to the presented results, the supercurrent is realized by the motion of the ground-state electronic-charge distribution of the fully occupied band. The motion of the electronic-charge distribution is conditioned by the newly arisen, nondissipative degrees of freedom of nuclear, Jahn-Teller-like, microflows. The Meissner effect is also interpreted.
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  • 90
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  • 91
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    International Journal of Quantum Chemistry 43 (1992), S. 443-443 
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    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
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  • 92
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    International Journal of Quantum Chemistry 43 (1992), S. 449-461 
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    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A vibrational coupling model to treat the solvation effects in chemical reaction rate calculations is proposed and applied to the intramolecular hydrogen transfer reaction CH3O· → ·CH2OH in the condensed phase. The effect of solvation is taken into account in two ways: (1) the solvent effect on the activation energy of the reaction is simulated by including 39 surrounding water molecules, represented by fractional charges at the assumed atomic positions, in the potential energy surface calculation; and (2) the vibrational couplings between the 10 nearest solvent molecules and the molecules constituting the reaction system are explicitly included in a vibrational frequency calculation. RRKM theory with Miller's tunneling correction included is employed to calculate the rate constants. The effect of solvation causes a significant change in the chemical reaction rate, mainly through a lowering of the activation energy. The vibrational coupling causes a slight increase of the rate constant in the tunneling region by perturbing the vibrational frequencies of the reactant and transition states, which appear in the rate-constant expression, but has little effect at higher temperatures.
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    International Journal of Quantum Chemistry 43 (1992), S. 511-529 
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    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The sulfur mustard, HD, a chemical warfare agent, has been studied by ab initio quantum molecular computations (HF/6-31G* and 6-31G) on its various forms (neutral, ethylene sulfonium, and free carbonium ions). The geometries of these molecules have been completely optimized and the minimal energy conformations determined with their associated charge distributions. We discuss these results on electrostatic properties with respect to the mechanism of DNA alkylation by HD and compare them with our previous study of the nitrogen mustard mechlorethamine.
    Additional Material: 6 Ill.
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  • 94
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    Electronic Resource
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 43 (1992), S. 531-550 
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A new method is presented for calculating the normalization factor for continuous spectrum functions in the L2 basis. One variant of this method is applicable to operators given in the form of a tridiagonal matrix and does not require explicit calculation of the roots of the characteristic equation. The other variant of the method can be used in the general case, where after the basis is introduced, its length is gradually increased.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
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  • 95
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 43 (1992) 
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
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  • 96
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 43 (1992), S. 579-589 
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Four esters of 5-cyano-1,6-dihydro-6-oxo-3-pyridinecarboxylic acid involving substitutions of methyl, isopropyl, tert-butyl, and phenyl groups at the 2-position, which exhibit varying degrees of cardiotonic activities, have been studied using the electric-field and electrostatic potential mapping techniques. The net charge distributions in the molecules were obtained using the MNDO method. Electric-field mapping has been performed in three-dimension in order to obtain information about the possible structure-activity relationships of these compounds. The results show a prominent electric-field region in the methyl-substituted compound extending from near the oxygen atom O6 to near the methyl group. This fact and orientation of the electric field in this region, in view of the Erhardt model, may be related to the greater cardiotonic activity of the methyl-substituted molecule in comparison to those of the other molecules of this class. © 1992 John Wiley & Sons, Inc.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
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  • 97
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 43 (1992), S. 647-658 
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A general scheme is proposed for the study of the interrelations and transformations of flexible functional groups within the configuration space M of all possible chemical species of a fixed overall stoichiometry S. The methods presented provide a concise but sufficiently detailed description of the occurrence of various functional groups in different families of nuclear arrangements, as well as their transformations into one another during chemical reactions and conformational changes. The approach uses experimental information on the importance of various functional groups, topological criteria for the flexibility of these functional groups, and the fundamental pattern of distribution of configurational families within the nuclear configuration space. The resulting schemes have simple, easily programmable representations. © 1992 John Wiley & Sons, Inc.
    Type of Medium: Electronic Resource
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  • 98
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 43 (1992), S. 669-676 
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The cycloaddition reaction of ketene and methylenimine, leading to 2-azetidinone, has been studied theoretically by RHF/3-21G and IRC. This reaction is believed to be nonsynchronous and concerted, taking place through a twisted transition state. Four π orbitals are involved in this reaction, which is a “2 × [1 + 1]”-type cycloaddition. In the course of the reaction, rotation of the methylene group instead of oxygen in ketene was ascertained. The activated barrier is calculated to be 33.9 kcal/mol. © 1992 John Wiley & Sons, Inc.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
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  • 99
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 43 (1992), S. 677-699 
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Two things were done in this paper: (i) A generalization of Schwinger's variational principle to a subsystem was developed within the framework of quantum field theory and applied to the theory of atoms in molecules. This work generalizes the previous derivation given in the Schrödinger formulation. (ii) It is demonstrated that Feynman's path integral, when expressed in terms of the coherent-state representation, can be constructed for a subsystem of a many-electron system if a divergence term, which serves as a variational constraint in the definition of an atom in a molecule, is added to the Lagrangian. This formulation is equivalent to the atomic statement of the variational principle if the divergence term is suitably constructed. It is shown that the path integral can be expressed as a product of the individual atomic contributions to the steps along the paths with the action being determined by a corresponding sum of the atomic contributions to the action integral. © 1992 John Wiley & Sons, Inc.
    Additional Material: 1 Ill.
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  • 100
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 43 (1992), S. 701-712 
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The total (elastic plus inelastic) intensities of 51 keV electrons scattered by H2CO and H2CCO have been measured over a range of K = (4π/λ) sin(θ/2) = 1-9.5 Å-1 and compared with the theoretical intensities calculated with SCF and CI wave functions. Significant discrepancies are found between the experimental intensities and the theoretical ones based on the SCF wave functions. Most of the chemical binding and electron correlation effects observed in the total scattered intensities are reproduced by the theoretical intensities based on the CI wave functions calculated with the basis set including polarization functions on all atoms. © 1992 John Wiley & Sons, Inc.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
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