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QCMP038. 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
Converted by K. J. Tupper, QCPE
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.
This software differs from QCPE 339 in that
no output is written to the screen as in the
original program, and two files, INPUT and
OUTPUT, are opened for I/O of data. Thus, a
data file must be named INPUT in order to be
read. This may be changed by the user to
suit his individual needs by changing the
statement:
OPEN(5,FILE='INPUT',STATUS='OLD')
Also note that the output file is given a
status of NEW, so all existing files of this
name will be deleted by executing this
program. The name of the output file may
also be changed by the user by changing the
"OPEN(6, " statement. Data which the user
does not want written to the OUTPUT file may
be written to the screen by substituting a '
* ' for the number '6' in the appropriate
WRITE statements.
The software package includes a complete
version of QCPE 339 as well as the individual
subroutines. Sample input and the resulting
output are provided, as is the executable
program QCP339.EXE which was used to generate
the output. The software was compiled using
Microsoft FORTRAN-77, version 3.2, using an
8087 coprocessor. The data for cis and trans
(NO)2 are not included in the INPUT data file
but have been included in the file
CISTRANS.DAT.
FORTRAN 77 (Microsoft FORTRAN)
Lines of Code: 624
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