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Scaling Factors and Uncertainties for ab Initio Anharmonic Vibrational Frequencies

Published

Author(s)

Russell D. Johnson III, Karl K. Irikura, Raghu N. Kacker, Ruediger Kessel

Abstract

To predict the vibrational spectra of molecules, ab initio calculations are often used to compute harmonic frequencies, which are usually scaled by empirical factors as an approximate correction for errors in the force constants and for anharmonic effects. Anharmonic computations of fundamental frequencies are becoming more popular. We report scaling factors, along with their associated uncertainties, for anharmonic (second-order perturbation theory) predictions from HF, MP2, and B3LYP calculations using the 6-31G(d) and 6-31+G(d,p) basis sets. Different scaling factors are appropriate for low- and high-frequency vibrations. The method of analysis is based upon the Guide to the Expression of Uncertainty in Measurement, published by the International Organization for Standardization (ISO). 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.
Citation
Journal of Chemical Theory and Computation

Keywords

ab initio, anharmonic, computational chemistry, density functional theory, quantum chemistry, uncertainty, vibrational frequencies, virtual measurement

Citation

Johnson, R. , Irikura, K. , Kacker, R. and Kessel, R. (2009), Scaling Factors and Uncertainties for ab Initio Anharmonic Vibrational Frequencies, Journal of Chemical Theory and Computation (Accessed February 24, 2024)
Created August 21, 2009, Updated February 19, 2017