Fourth-order vibrational perturbation theory with the Watson Hamiltonian: Report of working equations and preliminary results
Abstract
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 (nk + 12), with nk 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. The paper concludes with numerical examples featuring the H2O, Si2C, and cyclic-C3H2 molecules.
Document Details
- Document Type
- Pub Defense Publication
- Publication Date
- Sep 18, 2018
- Source ID
- 10.1063/1.5040360
Entities
People
- Bryan Changala
- Devin A Matthews
- John F Stanton
- Justin Z. Gong
Organizations
- Air Force Office of Scientific Research
- Arnold and Mabel Beckman Foundation
- United States Department of Energy
- University of Colorado
- University of Florida
- University of Texas at Austin