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339. NCRDWC:A Program to Determine Vibration
Frequencies and Normal Modes of Vibration
by H. L. Sellers, L. B. Sims, Lothar Schafer, and D. E.
Lewis, Department of Chemistry, University of Arkansas,
Fayetteville, Arkansas 72701
The potential energy for vibration of a molecule is
expressed in terms of internal valence displacement
coordinates. The internal coordinates which are used
are bond stretching, valence angle bending, out-of-
plane bending, and torsion about chemical bonds. For
details, see the article by J. C. Decius in J. Chem.
Phys., 17, 1315 (1949).
As small displacements are involved, the potential
energy is expanded in the displacements from
equilibrium yielding:
The program accepts a general or simple valence force
field with force constants corresponding to the
previously mentioned internal coordinates as described
in Molecular Vibrations (New York: McGraw-Hill Book
Co., 1955), pp. 54-61, by Wilson, Decius, and Cross.
The program converts the potential energy matrix to one
which is appropriate to mass-weighted Cartesian
displacement coordinates, since this affords an
efficient solution for the frequencies.
FORTRAN IV (IBM 360/370)
Lines of Code: 624
Recommended Citation: H. L. Sellers et al., QCPE 11,
229 (1977).
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