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251. POTLSURF: A Program to Compute the Potential
Energy Surface between a Closed-Shell Molecule and an
Atom
by Sheldon Green, Goddard Institute for Space Studies,
New York City; and Roy G. Gordon, Department of
Chemistry, Harvard University, Cambridge, Massachusetts
02138
POTLSURF is a program to compute the interaction
potential energy surface between a closed-shell
molecule, A, and a closed-shell atom (or ion), B. The
electron gas model of Gordon and Kim1 is used, so that
the basic input is a description of the relative
orientations and charge distributions (i.e., wave
functions) of A and B.
The program assumes that A and B are described by
previously computed wave functions, and the following
cases are implemented. The function for atom B is
expanded in Slater-type orbitals: molecule A is either
(1) an atom described in the same manner as atom B, (2)
a linear molecule expanded in a Slater-type basis, or
(3) a polyatomic molecule expanded in an uncontracted
Gaussian-type basis. The program is modular, so that
it should be straightforward to incorporate a different
way of describing either A or B (for example, numerical
Hartree-Fock or Thomas-Fermi-Dirac charge densities for
atom B or Slater-type polyatomic functions for molecule
A). The code is almost entirely in FORTRAN for the IBM
360. For efficiency, Assembly language routines are
provided to suppress underflows and to compute cube
roots and the dot product; these may be replaced by
simple FORTRAN equivalents or eliminated by small
changes in the calling programs. The program fits into
200 Kb of core storage; no peripheral storage is
necessary. The core requirement can be reduced by use
of overlays or by dummying those routines which are not
needed for a specific program.
1. R. G. Gordon and Y. S. Kim, J. Chem. Phys., 56,
3122 (1972).
FORTRAN IV
Lines of Code: 2921
Recommended Citation: S. Green and R. G. Gordon, QCPE
11, 251 (1974).
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