✦ LIBER ✦

Basis set and correlation energy dependence of geometry and harmonic frequencies of difluoroethane, CHF2CH3

✍ Scribed by Martin Speis; Volker Buss

Publisher: John Wiley and Sons
Year: 1992
Tongue: English
Weight: 579 KB
Volume: 13
Category: Article
ISSN: 0192-8651
DOI: 10.1002/jcc.540130204

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✦ Synopsis

Abstract

Optimum geometries and harmonic frequencies calculated at the Hartree–Fock and the MP2 level are reported for the fluorohydrocarbon CHF~2~CH~3~; basis sets employed range from STO‐3G to 6‐311G**. The significantly shortened CC distance of 1.50 Å is reproduced already with the simplest split‐valence basis set; the CF distance of 1.36 Å on the other hand needs MP2 correction at least at the double‐ζ or 6‐311G* level. Symmetry coordinates defined in terms of internal coordinates are in qualitative agreement with available experimental evidence. Even the best basis set yields frequencies that differ from experimental (anharmonic) values by up to 200 cm^−1^ indicating the well‐known necessity of including higher‐order force constants if quantitative agreement with experiment is to be achieved.

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