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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) |