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639. ASYM40: A Program for Force Constant and Normal
Coordinate Analysis
by Lise Hedberg, Department of Chemistry, Oregon State
University, Corvallis, Oregon 97331 and Ian M. Mills,
Department of Chemistry, University of Reading, Reading
RG6 2AD, England
Program ASYM40 is a normal coordinate program which may
be used to refine force constants in the harmonic
approximation using the following experimental data:
wave numbers, isotopic wavenumber shifts, Coriolis
coupling constants, root-mean-square amplitudes of
vibration, and centrifugal distortion constants. The
name ASYM40 is intended to indicate that the
calculations may be carried out for molecules of any
symmetry with up to 40 atoms. The program has special
provisions for handling molecules of higher symmetry,
specifcally molecules with doubly and triply degenerate
normal modes.
The theory behind the calculations, and the way it is
implemented in the program, is discussed in the paper
by Lise Hedberg and Ian Mills, "ASYM20: A Program for
Force Constant and Normal Coordinate Calculations, with
a Critical Review of the Theory Involved", which is
scheduled for publication in the Journal of Molecular
Spectroscopy.
The refinement is usually carried out using symmetrized
force constants. For small molecules where there are
no redundancies, it is possible to carry out a
refinement based on valence force constants. If
redundancies are present, these must be eliminated
before the calculations can be carried out.
In an earlier version of the program the van der Waals
radii of atoms consist of internal data. In this
version these values are contained in a text file named
"VDW.DAT". Thus the user can edit this file in order
to change the radius of an atom or to add non-existing
values.
Lines of Code: 6791
FORTRAN 77 (VAX)
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