Prediction of Vibrational Spectra by Computational Chemistry
-Ab initio Molecular Orbital Calculation of Vibrational Frequencies and Infrared Intensities of Gas Phase Dichloromethane Molecules CH2Cl2, CHDCl2 and CD2Cl2-

Kazutoshi TANABEa*, Takatoshi MATSUMOTOb and Seiji TSUZUKIa

aNational Institute of Advanced Industrial Science and Technology
1-1-1 Umezono, Tsukuba, Ibaraki 305-8568, Japan
bIMRAM, Tohoku University
2-1-1 Katahira, Aoba-ku, Sendai, Miyagi 980-8577, Japan

(Received: January 17, 2002; Accepted for publication: February 15, 2002; Published on Web: April 24, 2002)

Vibrational frequencies and infrared intensities of dichloromethane molecules CH2Cl2, CHDCl2, CD2Cl2 in the gas phase have been calculated using the ab initio molecular orbital method with many combinations of basis set functions and electron correlation correction methods, and compared with experimental values. The dependence of calculated frequencies and intensities on basis set function and electron correlation correction method was made clear, and as a recommended combination of basis set function and electron correlation correction method, MP2/6-311G(3df,3pd) was proposed and gave an average error of 0.93% for vibrational frequency calculation, and MP2/D95(3df,3pd) was proposed to give an average error of 22.9% for infrared intensity calculation. However, there are numerous difficulties in the theoretical analysis of vibrational spectra when using computational chemistry methods.

Keywords: Vibrational spectra, Molecular orbital methods, Vibrational frequencies, Infrared intensities, Dichloromethane

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