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[Licence| Download | New Version Template] abbd_v2_0.gz(561 Kbytes)
Manuscript Title: POLYRATE 4: a new version of a computer program for the calculation of chemical reaction rates for polyatomics.
Authors: 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, D.G. Truhlar
Program title: POLYRATE 4.0.1
Catalogue identifier: ABBD_v2_0
Distribution format: gz
Journal reference: Comput. Phys. Commun. 71(1992)235
Programming language: Fortran.
Computer: Cray-2, Cray Y-MP8/864, Cray X-MP-EA/4-64, Silicon Graphics IRIS-4D/310GTX, Sun SPARCStation 4/360, IBM RS/6000-550, VAX 6000-510, VAX 11/780.
Operating system: UNICOS 6.1, UNICOS 6.1.5, IRIX System 4.0.1, SunOS 4.1.1, AIX 3.1.5, VMS 5.4&4.3.
RAM: 1222K words
Word size: 64
Peripherals: disc.
Keywords: Molecular physics, Chemical kinetics, Activation energy, Stationary-point Analysis, Reaction path, Variational transition State theory, Small-curvature Tunneling, Large-curvature Tunneling, 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) from analytic potential energy functions or electronic structure input files. 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 or reactants, products, and transition states and to and to calculate multidimensional semiclassical tunneling probabilities and transmission coefficients.

Solution method:
Rate constants may be calculated using either conventional or variational transition state theory. A number of methods are available for calculating the reaction path and for treating anharmonicity of the vibrational modes of the reactants, products, and generalized transition-state species, all under the assumption of independent normal modes. Both small-curvature and large-curvature multidimensional semiclassical tunneling methods are available as options to calculate tunneling contributions to transmission coefficients.

Reasons for new version:
The new version is greatly enhanced in terms of capabilities, ease of redimensioning, convenience of interfacing with user-supplied analytic potential energy functions, and portability. In addition all COMMON blocks are now byte aligned. The most inportant new capabilities are reactions at gas-solid interfaces, improved reaction-path algorithms, large-curvature semiclassical tunneling calculations, the centrifugal- dominant version of the small-curvature semiclassical adiabatic tunneling approximation, a hindered-internal-rotator anharmonicity option, and the capability to use information from an electronic structure input file instead of an analytic potential energy surface.

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 only with analytic potential energy functions.

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 rate constants. The program is distributed with an on-line documentation file in portable ASCII text format and with user-friendly scripts for creating INCLUDE files, compiling, linking, and executing in interactive or batch modes.

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 28 gas-phase test runs distributed with the program, the average computer time for these 28 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 range     gas-phase average    gas-solid times   
 Cray-2          0.4-197               58                 252,471        
 Y-MP            0.3-129               39                 163,283        
 X-MP            0.3-172               52                 228,427        
 IBM RS/6000     0.5-223               60                 184,486        
 IRIS            0.6-913              179                 578,1252       
 SPARCStation    1.6-1919             427                 1373,2860      
 VAX 6000-510    3.5-1167             278                 815,2103       
 VAX 11/780      21.5-15741          3604                 10421,25975