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  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Journal of structural chemistry 21 (1980), S. 266-271 
    ISSN: 1573-8779
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Journal of structural chemistry 23 (1982), S. 167-170 
    ISSN: 1573-8779
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 1573-8779
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Springer
    Theoretical and experimental chemistry 26 (1990), S. 5-9 
    ISSN: 1573-935X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract We propose a dynamic shift method for the levels of the Brillouin states, providing reliable and sufficiently rapid convergence of the iteration process in the CASSCF method with optimization of the orbitals according to the super-CI scheme. In each step of the super-CI procedure, the shift parameters are determined automatically and individually for each Brillouin state. The proposed method is simple and easy to carry out. It also guarantees that a physically incorrect solution cannot appear. The method was carried out using the CASSCF programming package; for the example of specific calculations for the1Σ+ state of the TiO molecule, we show that the method is efficient and preferred.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    Springer
    Theoretical and experimental chemistry 27 (1991), S. 396-399 
    ISSN: 1573-935X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Using the self-consistent field method in the full active space (SCF FAS) and the Gaussian basis we calculate 11 lowest electronic states of the TiF molecule, which has been little studied experimentally. We show that thel 2Δ state lies higher than the ground X4Φ state by no more than 4000 cm−1.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 30 (1986), S. 509-541 
    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 modern version of the process of removing redundant variables in an MCSCF optimization problem is studied on the basis of the manifold theory. It is shown that there exists a simple parametrization of the MCSCF orbital manifold that is convenient for computer implementation of quasi-Newton optimization schemes. A sequential unconstrained optimization technique for minimizing electronic energy with respect to local coordinates is described.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 43 (1992), S. 827-853 
    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 second-order version of the CASSCF approach to the optimization problem for a single (ground or excited) state and a group of excited states (involving, if necessary, also the ground state) is proposed. In contrast to the already existing methods, in the frameworks of our approach, there arises no need in completing the set of states to be optimized to the full basis set of configuration function space. Generation of secondary orbitals in the course of orbital optimization is also not required. All necessary integral transformations are performed only with active orbitals. These certainly attractive features of our approach appear due to employing the Gauss parametrization of average electronic energy domain, which is nonstandard in quantum chemistry. © 1992 John Wiley & Sons, Inc.
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 54 (1995), S. 329-336 
    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: Convergence properties of the augmented Hessian (AH) method when searching for stationary points of an arbitrary fixed index are investigated. It is shown that the displacement vector of this method is proportional to one of the Hessian eigenvectors if the current point is far from a stationary one of the required index. A simple and reliable criterion for nearness of the current point to a stationary one of the desired index is proposed. The efficiency of a new one-dimensional optimization scheme that uses this criterion is studied. The case of coincidence of Hessian eigenvalues, which is a bottleneck of the standard AH method, is analyzed. A relation of the AH method to those by Poppinger and Wales is outlined. The correctness of the results obtained is illustrated on an example of a model surface. © 1995 John Wiley & Sons, Inc.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
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  • 9
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 58 (1996), S. 461-469 
    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 possibility of stabilization in an external homogeneous electric field on the HeH2(21 A′) metastable state relative to its nonadiabatic decay into the 1 1A′ state is investigated theoretically. If the lowest vibrational levels of the HeH2 (2 1A′) state might be stabilized, one would try to detect the radiative transition 1 1A′ ← 2 1A′ from these levels and thus to verify experimentally the existence of the HeH2 (2 1A′) state. It is shown that the separation between the potential energy surfaces (PESs) of the states in question and the energy of their avoided crossing point do increase in the field. Moreover, it is shown that in the fields with strength up to 107 V/cm the nonadiabatic decay of the 2 1A′ state along one of the vibrational modes may be closed. However, along two other modes such decay still may occur. It is noted nevertheless that the question of such stabilization possibility in inhomogeneous fields (i.e., in ionic crystal or on its surface) is still open. The effect of the field was taken into account within an analytic two-level model. The unperturbed PESs were calculated by the CASSCF method. © 1996 John Wiley & Sons, Inc.
    Additional Material: 10 Ill.
    Type of Medium: Electronic Resource
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