Force field calculation for inplane vibrations of ethylene usingcndo/Force method |
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Authors: | A Jothi G Shanmugam A Annamalai Surjit Singh |
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Institution: | (1) Department of Crystallography and Biophysics, University of Madras, Guindy Campus, 600 025 Madras, India;(2) Department of Chemistry, Indian Institute of Technology, 600 036 Madras, India |
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Abstract: | cndo/Force method is used to evaluate redundancy-free internal valence force field (rfivff) for inplane vibrations of ethylene. The bending force constants, the stretch-band and bend-bend interaction force constants
are predicted reasonably well in magnitude and sign by this method; whereas stretching force constants and stretch-stretch
interactions are overestimated. Initial force field is set up by transferring stretching force constants from structurally-related
molecules and including the rest of the force constants fromcndo force field. The field so constructed is subjected to refinement by the least square method. A total of 64 vibrational frequencies
of C2H4, C2D4, C2H2D2 and their13C isotopic modifications are used to determine force field containing 15 parameters. The final force field is found to be
reasonable on the basis of frequency fits, potential energy distribution and band assignments. |
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Keywords: | Force field normal coordinate analysis ethylene inplane vibrations cndo/Force method" target="_blank">cndo/Force method |
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