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

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.

[1]  B. C. Garrett,et al.  Variational transition state theory and tunneling for a heavy–light–heavy reaction using an ab initio potential energy surface. 37Cl+H(D) 35Cl→H(D) 37Cl+35Cl , 1983 .

[2]  K. Laidler,et al.  Vibrationally Adiabatic Model for the Dynamics of H+H2 Systems , 1970 .

[3]  Donald G. Truhlar,et al.  EXACT TUNNELING CALCULATIONS. , 1971 .

[4]  D. Truhlar,et al.  Interpolated variational transition-state theory: Practical methods for estimating variational transition-state properties and tunneling contributions to chemical reaction rates from electronic structure calculations , 1991 .

[5]  D. Truhlar,et al.  Ab initio transition state theory calculations of the reaction rate for OH+CH4→H2O+CH3 , 1990 .

[6]  Samuel Glasstone,et al.  The Theory Of Rate Processes , 1941 .

[7]  H. Schwarz.  Numerical Analysis , 1989 .

[8]  M. Gordon,et al.  From Force Fields to Dynamics: Classical and Quantal Paths , 1990, Science.

[9]  J. Stewart.  Optimization of parameters for semiempirical methods I. Method , 1989 .

[10]  Donald G. Truhlar,et al.  Generalized transition state theory. Classical mechanical theory and applications to collinear reactions of hydrogen molecules , 1979 .

[11]  B. C. Garrett,et al.  Test of variational transition state theory and the least-action approximation for multidimensional tunneling probabilities against accurate quantal rate constants for a collinear reaction involving tunneling into an excited state , 1985 .

[12]  D. Truhlar,et al.  Variational transition state theory calculations for an atom--radical reaction with no saddle point: O+OH , 1983 .

[13]  Donald G. Truhlar,et al.  Generalized transition state theory. Bond energy-bond order method for canonical variational calculations with application to hydrogen atom transfer reactions , 1979 .

[14]  B. C. Garrett,et al.  Application of the large-curvature tunneling approximation to polyatomic molecules: Abstraction of H or D by methyl radical , 1989 .

[15]  D. Truhlar,et al.  Direct dynamics calculations with NDDO (neglect of diatomic differential overlap) molecular orbital theory with specific reaction parameters , 1991 .

[16]  M. Dewar,et al.  Ground States of Molecules. 38. The MNDO Method. Approximations and Parameters , 1977 .

[17]  Mark S. Gordon,et al.  Algorithms and accuracy requirements for computing reaction paths by the method of steepest descent , 1988 .

[18]  Donald G. Truhlar,et al.  POLYRATE: A general computer program for variational transition state theory and semiclassical tunneling calculations of chemical reaction rates , 1987 .

[19]  John E. Adams,et al.  Reaction path Hamiltonian for polyatomic molecules , 1980 .

[20]  H. Johnston.  Gas Phase Reaction Rate Theory , 1966 .

[21]  B. C. Garrett,et al.  Incorporation of quantum effects in generalized-transition-state theory , 1982 .

[22]  Kazuhiro Ishida,et al.  The intrinsic reaction coordinate. An ab initio calculation for HNC→HCN and H−+CH4→CH4+H− , 1977 .

[23]  Mark S. Gordon,et al.  The Intrinsic Reaction Coordinate and the Rotational Barrier in Silaethylene , 1985 .

[24]  B. C. Garrett,et al.  Variational Transition State Theory , 1980 .

[25]  Eamonn F. Healy,et al.  Development and use of quantum mechanical molecular models. 76. AM1: a new general purpose quantum mechanical molecular model , 1985 .

[26]  Donald G. Truhlar,et al.  Optimized calculations of reaction paths and reaction‐path functions for chemical reactions , 1992 .

[27]  B. C. Garrett,et al.  Generalized transition state theory. Quantum effects for collinear reactions of hydrogen molecules and isotopically substituted hydrogen molecules , 1979 .

[28]  Peter R. Taylor,et al.  Accurate quantum chemical calculations , 2007 .

[29]  David L. Beveridge,et al.  Approximate molecular orbital theory , 1970 .

[30]  Warren J. Hehre,et al.  AB INITIO Molecular Orbital Theory , 1986 .

[31]  Donald G. Truhlar,et al.  Polyatomic canonical variational theory for chemical reaction rates. Separable‐mode formalism with application to OH+H2→H2O+H , 1982 .

[32]  W. Miller.  Unified statistical model for ’’complex’’ and ’’direct’’ reaction mechanisms , 1976 .

[33]  Donald G. Truhlar,et al.  Criterion of minimum state density in the transition state theory of bimolecular reactions , 1979 .

[34]  Donald G. Truhlar,et al.  Improved treatment of threshold contributions in variational transition-state theory , 1980 .

[35]  J. Stewart.  Optimization of parameters for semiempirical methods II. Applications , 1989 .

[36]  Michael Baer,et al.  Theory of chemical reaction dynamics , 1985 .

[37]  B. C. Garrett,et al.  Phenomenological manifestations of large-curvature tunneling in hydride-transfer reactions , 1986 .

[38]  Donald G. Truhlar,et al.  POLYRATE 4: A new version of a computer program for the calculation of chemical reaction rates for polyatomics , 1992 .

[39]  B. C. Garrett,et al.  Improved canonical variational theory for chemical reaction rates. Classical mechanical theory and applications to collinear reactions , 1980 .

[40]  D. Truhlar,et al.  Temperature dependence of the kinetic isotope effect for a gas-phase SN2 reaction: Cl- + CH3Br , 1991 .

[41]  Michael J. S. Dewar,et al.  Ground states of molecules. XXVI. MINDO/3 calculations for hydrocarbons , 1975 .

[42]  Michael Page,et al.  On evaluating the reaction path Hamiltonian , 1988 .

[43]  Michael J. S. Dewar,et al.  Development and use of quantum molecular models. 75. Comparative tests of theoretical procedures for studying chemical reactions , 1985 .

[44]  B. C. Garrett,et al.  A general small-curvature approximation for transition-state-theory transmission coefficients , 1981 .

[45]  M. Gordon,et al.  Ab initio reaction paths and direct dynamics calculations , 1989 .

[46]  Rudolph A. Marcus,et al.  Analytical Mechanics of Chemical Reactions. III. Natural Collision Coordinates , 1968 .

[47]  Donald G. Truhlar,et al.  Generalized transition state theory calculations for the reactions D+H2 and H+D2 using an accurate potential energy surface: Explanation of the kinetic isotope effect , 1980 .

[48]  Mark S. Gordon,et al.  Potential energy surfaces for polyatomic reaction dynamics , 1987 .

[49]  J. Hirschfelder,et al.  General Collision Theory Treatment for the Rate of Bimolecular, Gas Phase Reactions , 1959 .