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  • 1
    Electronic Resource
    Electronic Resource
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 111 (1999), S. 8987-8999 
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Molecular-dynamics simulations of the photoisomerization of cis-stilbene in supercritical argon were performed. The stilbene molecule is represented by ab initio quantum chemistry, while the solvent, the interaction with solvent, and the time evolution were described by classical mechanics. Reaction rate constants are estimated and their dependence on temperature, pressure, and viscosity are investigated. Agreement with available experimental data was obtained. Our simulations strongly suggest a minimum on the excited-state potential-energy surface at a gauche conformation which is very rapidly reached after excitation, which leads to nonequilibrium barrier transitions. Specific solvent effects were identified. Implications on the current opinion on stilbene photoisomerization are discussed. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 108 (1998), S. 8773-8781 
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: An interpolation scheme for potential energy surfaces is presented. It employs a regular grid and finite element interpolation. The aim is the reduction of the computational expense for molecular dynamics simulation with a quantum chemical potential energy function. The methods used are described in detail. The feasibility is demonstrated and the efficiency and accuracy are evaluated for the photoisomerization of cis-stilbene in supercritical argon, using an ab initio configuration- interaction treatment for the first electronically excited state of the stilbene molecule and classical force fields for the solvent–solute interactions (quantum mechanical/molecular mechanical molecular dynamics). The number of required quantum chemical calculations of energy and gradients was substantially reduced compared to a simulation not using the interpolation scheme. On the other hand, the impact on the accuracy is insignificant. © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Computational Chemistry 18 (1997), S. 1484-1495 
    ISSN: 0192-8651
    Keywords: energy hypersurface interpolation ; force interpolation ; simplex ; molecular dynamics algorithm ; Monte Carlo algorithm ; Chemistry ; Theoretical, Physical and Computational Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Computer Science
    Notes: A method is presented to interpolate the potential energy function for a part of a system consisting of a few degrees of freedom, such as a molecule in solution. The method is based on a modified finite element (FE) interpolation scheme. The aim is to save computer time when expensive methods such as quantum-chemical calculations are used to determine the potential energy function. The expensive calculations are only carried out if the molecule explores new unknown regions of the conformation space. If the molecule resides in regions previously explored, a cheap interpolation is performed instead of an expensive calculation, using known neighboring points. We report the interpolation techniques for the energies and the forces of the molecule, the handling of the FE mesh, and an application to a simple test example in molecular dynamics (MD) simulations. Good performance of the method was obtained (especially for MD simulations with a preceding Monte Carlo mesh generation) without losing accuracy.   © 1997 John Wiley & Sons, Inc.   J Comput Chem 18: 1484-1495, 1997
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
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