Fourth-order vibrational perturbation theory with the Watson Hamiltonian: Report of working equations and preliminary results

Gong, Justin Z.; Matthews, Devin A.; Changala, P. Bryan; Stanton, John F.

doi:10.1063/1.5040360

Title: Fourth-order vibrational perturbation theory with the Watson Hamiltonian: Report of working equations and preliminary results

Journal Article · 18 September 2018 · Journal of Chemical Physics

DOI: https://doi.org/10.1063/1.5040360 · OSTI ID:1540231

Gong, Justin Z. ^[1];

^[2];

^[3];

^[4]

The Univ. of Texas at Austin, Austin, TX (United States)
The Univ. of Texas, Austin, TX (United States)
Univ. of Colorado, Boulder, CO (United States)
Univ. of Florida, Gainesville, FL (United States)

A derivation of fourth-order vibrational perturbation theory (VPT4) based on the Watson Hamiltonian in dimensionless rectilinear normal coordinates is presented. Terms that are linear and cubic in the (n_k + 1/2), with n_k being the zeroth-order harmonic oscillator quantum numbers, appear in fourth order and extend the much simpler second-order vibrational perturbation theory model. The rather involved expressions for the fourth-order terms are derived with Rayleigh-Schrödinger perturbation theory, the process of verifying their correctness is described, and a computer code to generate the VPT4 constants from the potential energy surface derivatives is provided. Here, the paper concludes with numerical examples featuring the H₂O, Si₂C, and cyclic-C₃H₂ molecules.

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Research Organization:: Univ. of Hawaii, Honolulu, HI (United States)

Sponsoring Organization:: USDOE Office of Science (SC); USDOE

Grant/Contract Number:: FG02-07ER15885

OSTI ID:: 1540231

Alternate ID(s):: OSTI ID: 1471270

Journal Information:: Journal of Chemical Physics, Vol. 149, Issue 11; ISSN 0021-9606

Publisher:: American Institute of Physics (AIP)Copyright Statement

Country of Publication:: United States

Language:: English

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