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QCMP149. DDRP-1: Program for Determining Dynamically
Defined Reaction Path (DDRP) in 3-Atom Collinear
Collision
by Gy. Dömötör and M. I. Bán, Institute of Physical
Chemistry, József Attila University, P. O. Box 105, H-
6701 Szeged, Hungary, and L. L. Stachó, Bolyai
Institute for Mathematics, József Attila University,
Aradi Vértanúk tere l, H-6720 Szeged, Hungary
This program is a realization of a global path
following procedures [1-5]. DDRP-1 requires the
positions of atoms in internal coordinates and can be
used for describing chemical reactions of collinear 3-
atom systems. For treating the most general case of
reacting systems using Cartesian coordinates, a
modified program (DDRP-2) will follow soon. The DDRP
procedure can be coupled with a conventional or quantum
chemical (semiempirical or ab initio) method suitable
for calculating the total energy of the system. In the
present version, the total energy is calculated by a
truncated MNDO program: QCPE 353 has been modified in
order to have a simpler input and reduce computational
time, and the configurational interaction has been
omitted. The DDRP programs approximate the reaction
path in an iterative way. A perfectly reliable choice
for the first approximation of the reaction path is a
closed polygon containing the probable location of the
saddle point in its interior. Regarding the high
stability of the method, this choice is safe but not
necessary.The approximate polygons computed in
consecutive steps show the rapid convergence of the
procedure: the polygons will quickly turn to a line,
thus giving the shape of the final reaction path. The
program in its present form is to illustrate the theory
laid down in the references cited and is suitable for
computing systems which are composed of atoms with
atomic numbers not greater than 17 and starting from
polygons with a maximum of 200 vertices. This latter
number is limited by the size of the RAM of PCs.
References:
[1] L. L. Stachó and M. I. Bán, Theor. Chim. Acta,
83, 433 (1991).
[2] L. L. Stachó and M. I. Bán, J. Math. Chem., 11,
405 (1992) .
[3] L. L. Stachó and M. I. Bán, Theor. Chim. Acta,
84, 535 (1993).
[4] L. L. Stachó and M. I. Bán, Computers Chem., 17,
21 (1993).
[5] Gy. Dömötör, M. I. Bán and L. L. Stachó, J. Comp.
Chem., l4, 1491 (1993).
Lines of Code: 3200
Microsoft FORTRAN (version 4.0 or later)
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