MORATE: a program for direct dynamics calculations of chemical reaction rates by semiempirical molecular orbital theory

Thanh N. Truong, Da hong Lu, Gillian C. Lynch, Yi Ping Liu, Vasilios S. Melissas, James J.P. Stewart, Rozeanne Steckler, Bruce C. Garrett, Alan D. Isaacson, Angels Gonzalez-Lafont, Sachchida N. Rai, Gene C. Hancock, Tomi Joseph, Donald G. Truhlar

Research output: Contribution to journalArticle

86 Scopus citations

Abstract

We present a computer program, MORATE (Molecular Orbital RATE calculations), for direct dynamics calculations of unimolecular and bimolecular rate constants of gas-phase chemical reactions involving atoms, diatoms, or polyatomic species. The potential energies, gradients, and higher derivatives of the potential are calculated whenever needed by semiempirical molecular orbital theory without the intermediary of a global or semiglobal fit. The dynamical methods used are conventional or variational transition state theory and multidimensional semiclassical approximations for tunneling and nonclassical reflection. The computer program is conveniently interfaced package consisting of the POLYRATE program, version 4.5.1, for dynamical rate calculations, and the MOPAC program, version 5.03, for semiempirical electronic structure computations. All semiempirical methods available in MOPAC, in particular MINDO/3, MNDO, AM1, and PM3, can be called on to calculate the potential and gradient. Higher derivatives of the potential are obtained by numerical derivatives of the gradient. Variational transition states are found by a one-dimensional search of generalized-transition-state dividing surfaces perpendicular to the minimum-energy path, and tunneling probabilities are evaluated by numerical quadrature.

Original languageEnglish (US)
Pages (from-to)143-159
Number of pages17
JournalComputer Physics Communications
Volume75
Issue number1-2
DOIs
StatePublished - Apr 1993

ASJC Scopus subject areas

  • Hardware and Architecture
  • Physics and Astronomy(all)

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    Truong, T. N., Lu, D. H., Lynch, G. C., Liu, Y. P., Melissas, V. S., Stewart, J. J. P., Steckler, R., Garrett, B. C., Isaacson, A. D., Gonzalez-Lafont, A., Rai, S. N., Hancock, G. C., Joseph, T., & Truhlar, D. G. (1993). MORATE: a program for direct dynamics calculations of chemical reaction rates by semiempirical molecular orbital theory. Computer Physics Communications, 75(1-2), 143-159. https://doi.org/10.1016/0010-4655(93)90172-9