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Manuscript Title: MORATE 6.5: A new version of a computer program for direct dynamics calculations of chemical reaction rate constants.
Authors: W.-P. Hu, G.C. Lynch, Y.-P. Liu, I. Rossi, J.J.P. Stewart, R. Steckler, B.C. Garrett, A.D. Isaacson, D.-h. Lu, V.S. Melissas, D.G. Truhlar
Program title: MORATE, version 6.5/P6.5-M5.05mn
Catalogue identifier: ACLM_v2_0
Distribution format: tar.gz
Journal reference: Comput. Phys. Commun. 88(1995)344
Programming language: Fortran.
Computer: Cray-2, Cray X-MP-EA, Cray C90, Silicon Graphics IRIS Indigo R4000, Sun SPARCStation IPX, IBM RS/6000-550.
Operating system: UNICOS 7.C.3, IRIX V.4 REL 5.2, SUNOS 4.1.2, AIX 3.2.5.
RAM: 3.6M words
Word size: 64
Peripherals: disc.
Keywords: Molecular physics, Reaction rates chemical, Activation energy, Stationary-point Analysis, Reaction path, Transition state theory, Tunneling, Chemical kinetics, Direct dynamics, Molecular orbital theory.
Classification: 16.12.

Nature of problem:
The program calculates chemical reaction rate coefficients for uni- molecular or bimolecular gas-phase reactions. Rate constants can be computed for canonical or microcanonical ensembles or for specific vibrational states of selected modes with translational, rotational and other vibrational modes in thermal equilibrium.

Solution method:
Rate constants may be calculated using conventional and/or variational transition state theory with multidimensional semiclassical tunneling contributions [1-3]. Instead of using an analytic potential energy surface, energies, gradients and hessians are obtained by semiempirical molecular orbital calculations [4-9]. The data needed for generalized transition state theory and tunneling calculations may optionally be "corrected" by interpolation [10,11] of higher-level data read from an external file. First the program optimizes the geometries of the reactant(s), conventional transition state (if any exists) and product(s). Then the minimum energy path is calculated by one of several methods. The variational transition state of canonical variational theory, improved canonical variational theory and/or micro- canonical variational theory is found by interpolation of data stored on a grid. Tunneling probabilities are calculated semiclassically by one or more methods, including the Wigner approximation, adiabatic methods for zero or small curvature of the reaction path, the large-curvature (version 3) tunneling method and/or the microcanonical optimized multi- dimensional tunneling approximation. MORATE also calculates the equilibrium constant for the reaction and it has an option to perform short runs in which conventional transition state theory rate constants are calculated without calculating a reaction path.

Summary of revisions:
The most important new capabilities since version 4.5 (the previous version described in CPC) are:
  1. The code has been made portable. It now runs on workstations as well as supercomputers.
  2. The VTST-IC method (dual-level direct dynamics) has been added.
  3. Input has been converted to keyword form.
  4. The canonical and microcanonical optimized multidimensional tunneling approximations have been included.
  5. An option has been added to allow quantization of the reaction- coordinate motion for unimolecular reactions.
  6. Output has been cleaned up and reformatted.
  7. The scripts for compilation and job submission have been improved.
  8. The eigenvector-following algorithm [12] for optimizing geometries has been added.
  9. New options for configuration interaction have been added.
A complete revision history is given in the manual.

The maximum number of atoms, heavy atoms and hydrogens allowed can be changed by resetting the NATOMS, MAXHEV and MAXLIT parameters, respectively. Reactions involving up to two reactants and two products are allowed. Lare-curvature tunneling is supported only in the harmonic approximation.

Unusual features:
The code is distributed with five documentation files containing instructions for input and other useful information for users. One is the MORATE manual, which does not repeat most of the material in the POLYRATE and MOPAC manuals; the second is the MOPAC-version 5.05mn manual, which does not repeat most of the material in the MOPAC-version 5.0 manual. The third and fourth documentation files are the POLYRATE- version 6.5 and MOPAC-version 5.0 manuals. The fifth file is a MORATE version of the input chapter of the POLYRATE manual containing the expanded input options available in MORATE that are not in the POLYRATE manual.

Running time:
This depends strongly on the particular system studied. For the twelve test runs distributed with the code, the computation times (in CPU seconds, in single-processor mode on the Cray X-MP-EA) range from 10 seconds for a 9-atom conventional transition state theory run to 5000 seconds for a 6-atom LCG3 calculation and from 0.3 seconds for a 6-atom variational transition state theory restart run to 200 seconds for a 6-atom LCG3 restart run.

[1] D.G. Truhlar and B.C. Garrett, Acc. Chem. Res. 13(1980)440.
[2] D.G. Truhlar and B.C. Garrett, Annu. Rev. Phys. Chem. 35(1984)159.
[3] S.C. Tucker and D.G. Truhlar, in: Supercomputer Algorithms for Reactivity, Dynamics and Kinetics of Small Molecules, ed. A. Lagana (Kluwer, Dordrecht, The Netherlands, 1989), p. 131.
[4] J.A. Pople and D.L. Beveridge, Approximate Molecular Orbital Theory (McGraw-Hill, New York, 1970).
[5] R.C. Bingham, M.J.S. Dewar and D.H. Lo, J. Amer. Chem. Soc. 97(1975)1294.
[6] M.J.S. Dewar and W. Thiel, J. Amer. Chem. Soc. 99(1977)4899.
[7] M.J.S. Dewar, E.G. Zoebisch, E.F. Healy and J.J.P. Stewart, J. Amer. Chem. Soc. 107(1985)3902.
[8] J.J.P. Stewart, J. Comp. Chem. 10(1989)221.
[9] J.J.P. Stewart, J. Computer-Aided Molecular Design 4(1990)1.
[10] W.-P. Hu, Y.-P. Liu and D.G. Truhlar, J. Chem. Soc. Faraday Trans. 90(1994)1715.
[11] J.C. Corchado, J. Espinosa-Garcia, W.-P. Hu, I. Rossi and D.G. Truhlar, J. Phys. Chem. 99(1995)687.
[12] J. Baker, J. Comp. Chem. 7(1986)385.