Getting down to the Fundamentals of Hydrogen Bonding: Anharmonic Vibrational Frequencies of (HF)2 and (H2O)2 from Ab Initio Electronic Structure Computations

• Published in: Journal of chemical theory and computation Vol. 10; no. 12; pp. 5426 - 5435
• Main Authors: Howard, J. Coleman, Gray, Jessica L, Hardwick, Amanda J, Nguyen, Linh T, Tschumper, Gregory S
• Format: Journal Article
• Language: English
• Published: United States American Chemical Society 09.12.2014
• ISSN: 1549-9618; 1549-9626
• DOI: 10.1021/ct500860v

This work presents a systematic investigation into the basis set convergence of harmonic vibrational frequencies of (H2O)2 and (HF)2 computed with second-order Møller–Plesset perturbation theory (MP2) and the coupled-cluster singles and doubles method with perturbative connected triples, CCSD­(T), while employing correlation-consistent basis sets as large as aug-cc-pV6Z. The harmonic vibrational frequencies presented here are expected to lie within a few cm–1 of the complete basis set (CBS) limit. For these important hydrogen-bonding prototype systems, a basis set of at least quadruple-ζ quality augmented with diffuse functions is required to obtain harmonic vibrational frequencies within 10 cm–1 of the CBS limit. In addition, second-order vibrational perturbation theory (VPT2) anharmonic corrections yield CCSD­(T) vibrational frequencies in excellent agreement with experimental spectra, differing by no more than a few cm–1 for the intramonomer fundamental vibrations. D 0 values predicted by CCSD­(T) VPT2 computations with a quadruple-ζ basis set reproduce the experimental values of (HF)2 and (H2O)2 to within 2 and 21 cm–1, respectively.