Following steepest descent reaction paths. The use of higher energy derivatives withabinitioelectronic structure methods

Autor:	James W. McIver, Charles Doubleday, Michael Page
Rok vydání:	1990
Předmět:	Chemistry Mathematical analysis General Physics and Astronomy Curvature symbols.namesake Classical mechanics Ab initio quantum chemistry methods Saddle point symbols Taylor series Physical and Theoretical Chemistry Gradient descent Series expansion Hamiltonian (quantum mechanics) Arc length
Zdroj:	The Journal of Chemical Physics. 93:5634-5642
ISSN:	1089-7690 0021-9606
DOI:	10.1063/1.459634
Popis:	New methods of determining the steepest descent reaction path in dynamical calculations based on the reaction path Hamiltonian are investigated. These methods use first and second energy derivatives and are correct to third order in the Taylor series expansion of the path in the arc length. The reaction H+H2O→H2+OH using small basis set three electron‐three active orbital CASSCF wave functions with first and second analytically calculated energy derivatives is used as a test platform. Reaction paths using a number of different step sizes are computed and their accuracy determined by evaluating the deviations of the computed path curvature from the exact curvature and the RMS deviation of the computed transverse frequencies from the exact values, criteria more sensitive and more relevant to dynamical studies than are geometrical parameters. The new methods are compared to one another in computational efficiency and accuracy. For this example reaction and level of theory it is found that, in addition to being more accurate at any step size, the new methods are less expensive at any accuracy than those that utilize only first energy derivatives.
Databáze:	OpenAIRE
Externí odkaz:	https://explore.openaire.eu/search/publication?articleId=doi_________::61d12a1749f5a3b04bb7485588bc8250 https://doi.org/10.1063/1.459634 Zobrazit plný text záznamu