High-level ab initio potential energy surfaces and vibrational energies of H2CS

Andrey Yachmenev; Sergei N Yurchenko; Tristan Ribeyre; Walter Thiel

doi:10.1063/1.3624570

High-level ab initio potential energy surfaces and vibrational energies of H2CS

J Chem Phys. 2011 Aug 21;135(7):074302. doi: 10.1063/1.3624570.

Authors

Andrey Yachmenev¹, Sergei N Yurchenko, Tristan Ribeyre, Walter Thiel

Affiliation

¹ Max-Planck-Institut für Kohlenforschung, Kaiser-Wilhelm-Platz 1, D-45470 Mülheim an der Ruhr, Germany.

PMID: 21861565
DOI: 10.1063/1.3624570

Abstract

Six-dimensional (6D) potential energy surfaces (PESs) of H(2)CS have been generated ab initio using the recently proposed explicitly correlated (F12) singles and doubles coupled cluster method including a perturbational estimate of connected triple excitations, CCSD(T)-F12b [T. B. Adler, G. Knizia, and H.-J. Werner, J. Chem. Phys. 127, 221106 (2007)] in conjunction with F12-optimized correlation consistent basis sets. Core-electron correlation, high-order correlation, scalar relativistic, and diagonal Born-Oppenheimer terms were included as additive high-level (HL) corrections. The resulting 6D PESs were represented by analytical functions which were used in variational calculations of the vibrational term values below 5000 cm(-1). The best PESs obtained with and without the HL corrections, VQZ-F12(*HL) and VQZ-F12∗, reproduce the fundamental vibrational wavenumbers with mean absolute deviations of 1.13 and 1.22 cm(-1), respectively. A detailed analysis of the effects of the HL corrections shows how the VQZ-F12 results benefit from error cancellation. The present purely ab initio PESs will be useful as starting points for empirical refinements towards an accurate "spectroscopic" PES of H(2)CS.