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Manuscript Title: POLYRATE 6.5: A new version of a computer program for the calculation of chemical reaction rates for polyatomics.
Authors: R. Steckler, W.-P. Hu, Y.-P. Liu, G.C. Lynch, B.C. Garrett, A.D. Isaacson, V.S. Melissas, D.-h. Lu, T.N. Truong, S.N. Rai, G.C. Hancock, J.G. Lauderdale, T. Joseph, D.G. Truhlar
Program title: POLYRATE, version 6.5
Catalogue identifier: ABBD_v3_0
Distribution format: tar.gz
Journal reference: Comput. Phys. Commun. 88(1995)341
Programming language: Fortran.
Computer: Cray-2, Cray X-MP-EA/4-64, Cray C90, Silicon Graphics IRIS Indigo R4000, Sun SPARCStation IPX, IBM RS/6000-550, DEC Alpha.
Operating system: UNICOS 7.0.5, UNICOS 7.C.3, IRIX System V.4 Release 5.2, SUNOS 4.1.2, AIX 3.2.5, DEC Alpha.
RAM: 1.6M words
Word size: 64
Peripherals: disc.
Keywords: Molecular physics, Reaction rates chemical, Activation energy, Stationary-point Analysis, Reaction path, Variational transition State theory, Small-curvature Tunneling, Large Curvature tunneling, Chemical kinetics, Surface science.
Classification: 16.12.

Nature of problem:
The program calculates unimolecular and bimolecular chemical reaction rates of polyatomic species (and also of atoms and diatoms as special cases). Rate constants may be calculated for canonical or micro- canonical ensembles and for reactions in the gas phase or solid state or at gas-solid interfaces. In addition, rates may be calculated for adiabatic and diabatic reactions in which one or more of the vibrational modes is restricted to the ground state or to the first excited state, while the translational, rotational and remaining vibrational modes are treated thermally. The program may also be used to find stationary geometries of reactants, products and transition states and to calculate reaction paths, Arrhenius parameters and equilibrium constants.

Solution method:
Energies, gradients and hessians are obtained from analytic potential energy functions or electronic structure input data. A number of methods are available for calculating the reaction path. Generalized normal mode coordinates are obtained in Cartesian coordinates in the subspace orthogonal to translations, rotations and the gradient. Anharmonicity may be included under the assumption of independent generalized normal modes. Rate constants may be calculated using either conventional or variational transition state theory [1,2]. Small- curvature, large-curvature and optimized multidimensional semiclassical tunneling methods [3-5] are available as options to calculate tunneling contributions to transmission coefficients.

Reasons for new version:
To improve stability and efficiency, add new capabilities and make input preparation more user-friendly.

Summary of revisions:
The most important new capabilities since version 4.0.1 (the previous version described in CPC) are
  1. The tunneling calculations have been made more stable and efficient.
  2. The large-curvature tunneling method has been generalized to allow for a well on the product side of the reaction path in the exoergic direction.
  3. Dimension management has been made easier.
  4. The VTST-IC method (dual-level direct dynamics) [6,7] has been added.
  5. Input has been converted to keyword form.
  6. The canonical and microcanonical optimized multidimensional tunneling approximations have been included.
  7. An option has been added to allow quantization of the reaction- coordinate motion for unimolecular reactions.
  8. Output has been cleaned up and reformatted.
  9. The scripts for compilation and job submission have been improved.
  10. The manual has been improved and indexed.
A complete revision history is given in the manual. Versions 4.1-5.1 were prepared primarily by Yi-Ping Liu, Gillian Lynch, Wei-Ping Hu, Vasilios Melissas, Rozeanne Steckler, Bruce Garrett, Alan Isaacson and Don Truhlar. Versions 6.0-6.5 were prepared primarily by Rozeanne Steckler, Wei-Ping Hu, Alan Isaacson and Donald Truhlar.

Restrictions:
The program has PARAMETER control for the maximum number of atoms and maximum number of save points at which reaction-path information is saved; these are set in one of the INCLUDE files and several sample settings are included in the distributed version. Large-curvature tunneling is available only for thermal rate constants in the harmonic approximation and with analytic potential energy functions. The hindered-internal-rotator anharmonicity option is also supported in runs employing analytic potential energy functions or using the IVTST-0 method or both.

Unusual features:
A restart option is available in which the program writes properties it has calculated for the reactants, products, reaction paths and generalized transition states to a disk file. Subsequent runs of the program can read this file and then proceed directly to the calculation of transmission coefficients and rate constants. The program is distributed with a documentation file in portable Postscript format and with user-friendly C shell scripts for compiling, linking and executing in interactive or batch modes and for checking the test suite results.

Running time:
The running time varies quite a bit, depending mainly on the number of atoms, complexity of the potential, range of reaction coordinate examined, step sizes and options for anharmonicity and tunneling. The range of computer times in seconds for the 35 gas-phase test runs distributed with the program, the average computer time for these 35 runs and the range of computer times for the two gas-solid interface test runs distributed with the program on the seven computers tested (in all cases, the code was compiled with optimization "on" at the highest "safe" level and times refer to execution on a single processor) are given in the following table:
                                          
                     gas-phase          gas-phase             gas-solid  
                     (range)            (average)             (average)  
 Cray-2              0.7-149               27                   338      
 Cray C90            0.2-94                14                   155      
 Cray X-MP-EA        0.4-195               28                   201      
 IBM RS/6000         1.0-360               39                   351      
 IRIS                0.6-911               98                   694      
 SPARCStation        1.3-1883             204                  1688      
 DEC Alpha           0.5-296               35                   347      
 

References:
[1] B.C. Garrett, D.G. Truhlar, R.S. Grev and A.W. Magnuson, J.Chem.Phys. 84(1980)1730.
[2] D.G. Truhlar, A.D. Isaacson and B.C. Garrett, in: Theory of Chemical Reaction Dynamics, Vol. 4, ed. M. Baer (CRC Press, Boca Raton, FL, 1985) pp. 65-137.
[3] D.-h. Lu, T.N. Truong, V.S. Melissas, G.C. Lynch, Y.-P. Liu, B.C. Garrett, R. Steckler, A.D. Isaacson, S.N. Rai, G.C. Hancock, J.G. Lauderdale, T. Joseph and D.G. Truhlar, Computer Physics Communications 71(1992)235.
[4] Y.-P. Liu, G.C. Lynch, T.N. Truong, D.-h. Lu, D.G. Truhlar and B.C. Garrett, J. Amer. Chem. Soc. 115(1993)2408.
[5] Y.-P. Liu, D.-h. Lu, A. Gonzalez-Lafont, D.G. Truhlar and B.C. Garrett, J. Amer. Chem. Soc. 115(1993)7806.
[6] W.-P. Hu, Y.-P. Liu and D.G. Truhlar, J. Chem. Soc. Faraday Trans. 90(1994)715.
[7] J.C. Corchado, J. Espinosa-Garcia, W.-P. Hu, I. Rossi and D.G. Truhlar, J. Phys. Chem. 99(1995)687.