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  • 1
    Electronic Resource
    Electronic Resource
    Recurrence relations for the expansion of Slater-type orbitals about displaced centers (1986)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 85 (1986), S. 5890-5894 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: We show here that the coefficients for the expansion of any Slater-type function over a displaced center can be obtained by three simple (and numerically stable) recurrence relations starting at the expansion coefficients of the 1s or 2s orbitals. We present also compact (and very fast to compute) formulas for these initial quantities.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.451551
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  • 2
    Electronic Resource
    Electronic Resource
    Molecular integrals with Slater basis. III. Three-center nuclear attraction integrals (1991)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 94 (1991), S. 5032-5039 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: We discuss the calculation of the general three-center nuclear attraction integrals with Slater type orbitals using a one-center expansion method which exploits the algorithms previously developed by us for long-range integrals. From the analysis of the numerical stability, accuracy, and computational cost we conclude that the reported procedure is suitable for the calculation of these integrals with any desired precision. Moreover, we have found that most of these integrals can be obtained with high accuracy at a very low computational cost, but the procedure could be too expensive for a few of them.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.460538
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  • 3
    Electronic Resource
    Electronic Resource
    Molecular integrals with Slater basis. IV. Ellipsoidal coordinate methods for three-center nuclear attraction integrals (1992)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 97 (1992), S. 7613-7622 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: We develop and check an updated version of the ellipsoidal coordinate methods for the calculation of three-center nuclear attraction integrals with Slater-type orbitals (STOs). A first set of recurrence relations allows us to express these integrals in terms of some basic potentials. The basic potentials are classified in short- and long-range types, and then calculated in specific ways from auxiliary functions obtained by using a new set of both stable and fast recurrence relations. Numerical tests show that the procedure enables to reach very high accuracy in the integrals with a low computational cost.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.463481
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  • 4
    Electronic Resource
    Electronic Resource
    Analysis of the molecular density (1999)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 110 (1999), S. 4213-4220 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The minimal deformation criterion, previously proposed for the partition of the molecular density into atomic contributions, is updated and extended. For any Gaussian basis set, these atomic contributions are expanded in a series of real spherical harmonics by radial factors. The terms with l=0 determine the spherical parts of the atomic clouds and the remaining ones, their deformations. This detailed description is complemented with a simplified representation of the molecular density in terms of atomic charges and multipoles. Moreover, these descriptions give a simple way to calculate the electrostatic potential of the molecule as well as the electrostatic interaction between molecules. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.478303
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  • 5
    Electronic Resource
    Electronic Resource
    Simplified expansion of Slater orbitals about displaced centers (1988)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 34 (1988), S. 121-131 
    Details
    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 and very simple one-range expansion of the 0s function is derived and employed as the starting point of three recurrence relations which allow the expansion of arbitrary Slater functions over displaced centers. Convergence of the expansions, both pointwise and in norm, are analyzed, and three-center nuclear attraction integrals are chosen for a further test of the formal developments and the numerical behavior of these expansions.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/qua.560340205
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  • 6
    Electronic Resource
    Electronic Resource
    Calculation of integrals with slater basis from the one-range expansion of the 0s function (1990)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 37 (1990), S. 69-83 
    Details
    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 one-range expansion of the 0s-STO - previously reported by us - is employed to derive explicit expressions for the elements of auxiliary matrices - appearing in the calculation of one- and two-electron multicenter integrals with STOS - in the form of infinite series. Then, we are able to perform the formal summation of the series giving both closed expressions for these elements and several relations between them. A computational algorithm based on these formal developments is proposed and its numerical behavior is analyzed.
    Additional Material: 6 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/qua.560370106
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  • 7
    Electronic Resource
    Electronic Resource
    Transferability of atomic descriptions in molecules (1986)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 30 (1986), S. 671-684 
    Details
    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 a previous paper we proposed a new electrostatic description of the molecular electronic density in terms of charges, dipoles, quadrupoles, octupoles, etc. In this paper we apply this analysis to some first members of alkanic, ethylenic, acetylenic, alcoholic, aldehyde, amine, and nitrile series. Results show the clear transferability of the atomic descriptions for chemically similar atoms as well as the remarkable sensitivity of the electronic density versus changes in the basis sets, pointed out in our previous work. We discuss the calculation of molecular potentials from these atomic descriptions (and present an example) and some practical applications.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/qua.560300510
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  • 8
    Electronic Resource
    Electronic Resource
    Improved algorithm for the calculation of one-electron two-center integrals with STOs (1989)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Computational Chemistry 10 (1989), S. 869-874 
    Details
    ISSN: 0192-8651
    Keywords: Computational Chemistry and Molecular Modeling ; Biochemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Computer Science
    Notes: In a previous article (J. Fernández Rico, R. López and G. Ramírez, J. Comp. Chem., 9, 790 (1988)) we have proposed the calculation of molecular integrals involving STOs by means of some recurrence relations which use two sets (h and H) of overlap integrals (basic matrices). In the present paper, we derive explicit expressions of these integrals employing the two-range expansion of the 0s-function. This approach yields equations for the elements of the two basic matrices in terms of two further matrices, k(x,y) and i(x,y), and some auxiliary functions. Relations between the elements of these matrices and the functions are thoroughly explored and numerical tests are included for illustrating the behavior of the method.
    Additional Material: 2 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jcc.540100703
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  • 9
    Electronic Resource
    Electronic Resource
    Long-Range multicenter integrals with slater functions: Gauss transform-based methods (1993)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Computational Chemistry 14 (1993), S. 1203-1211 
    Details
    ISSN: 0192-8651
    Keywords: Computational Chemistry and Molecular Modeling ; Biochemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Computer Science
    Notes: The separation of the short- and long-range terms in the potentials generated by pairs of Slater functions is reformulated in the context of the Gauss transform method. Analytic expressions of the long-range potentials (in closed form) are derived for equal exponents and generalized (as expansion series) for different exponents. Additionally, the representation of these potentials from small sets of charges or lowest-order multipoles is examined, paying special attention to their values and optimal positions. Finally, numerical tests of the formal developments are presented. It is concluded that the long-range three- and four-center integrals can be calculated with high accuracy in a simple and relatively inexpensive manner. © John Wiley & Sons, Inc.
    Additional Material: 7 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jcc.540141010
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  • 10
    Electronic Resource
    Electronic Resource
    Restricted Hartree-Fock approximation. I. Techniques for the energy minimization (1983)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Computational Chemistry 4 (1983), S. 33-40 
    Details
    ISSN: 0192-8651
    Keywords: Computational Chemistry and Molecular Modeling ; Biochemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Computer Science
    Notes: We present a new procedure for direct minimization of the RHF energy, which presents advantages over SCF methods with respect to convergence rate and computational cost. In this procedure we combine several techniques with the aim of obtaining best directions and step lengths for the iterative search for a minimum of the energy. In this article we develop the theory. Therefore, we analyze the variational function; we present a short description of the minimization techniques and we discuss in detail the way in which they are to be used. The computational aspects of the procedure will be treated in the following article.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jcc.540040106
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