Anharmonic Vibrational Frequency Calculations Are Not Worthwhile for Small Basis Sets

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• 作者：Ruth L. Jacobsen ; Russell D. Johnson ; III ; Karl K. Irikura ; Raghu N. Kacker
• 刊名：Journal of Chemical Theory and Computation
• 出版年：2013
• 出版时间：February 12, 2013
• 年：2013
• 卷：9
• 期：2
• 页码：951-954
• 全文大小：228K
• 年卷期：v.9,no.2(February 12, 2013)
• ISSN：1549-9626

文摘

Anharmonic calculations using vibrational perturbation theory are known to provide near-spectroscopic accuracy when combined with high-level ab initio potential energy functions. However, performance with economical, popular electronic structure methods is less well characterized. We compare the accuracy of harmonic and anharmonic predictions from Hartree鈥揊ock, second-order perturbation, and density functional theories combined with 6-31G(d) and 6-31+G(d,p) basis sets. As expected, anharmonic frequencies are closer than harmonic frequencies to experimental fundamentals. However, common practice is to correct harmonic predictions using multiplicative scaling. The surprising conclusion is that scaled anharmonic calculations are no more accurate than scaled harmonic calculations for the basis sets we used. The data used are from the Computational Chemistry Comparison and Benchmark Database (CCCBDB), maintained by the National Institute of Standards and Technology, which includes more than 3939 independent vibrations for 358 molecules.