Vibration—rotation—tunneling dynamics calculations for the four-dimensional (HCl)2 system: A test of approximate models

Abstract

Several commonly used approximate methods for the calculation of vibration—rotation—tunneling spectra for (HCl)2 are described. These range from one-dimensional models to an exact coupled four-dimensional treatment of the intermolecular dynamics. Two different potential surfaces were employed–an ab initio and our ES1 experimental surface (determined by imbedding the four-dimensional calculation outlined here in a least-squares loop to fit the experimental data, which is described in the accompanying paper [J. Chem. Phys. 103, 933 (1995)]. The most important conclusion deduced from this work is that the validity of the various approximate models is extremely system specific. All of the approximate methods addressed in this paper were found to be sensitive to the approximate separability of the radial and angular degrees of freedom, wherein exists the primary difference between the two potentials. Of particular importance, the commonly used reversed adiabatic angular approximation was found to be very sensitive to the choice for fixed R; an improper choice would lead to results very much different from the fully coupled results and perhaps to false conclusions concerning the intermolecular potential energy surface.

Publisher

AIP Publishing

Publication Date

7-15-1995

Publication Title

Journal of Chemical Physics

Department

Chemistry and Biochemistry

Document Type

Article

DOI

https://dx.doi.org/10.1063/1.469793

Keywords

Hydrochloric acid, Vibrational states, Rotational states, Potential energy surfaces, Adiabatic approximation, Intermolecular forces, Hydrogen bonds, Tunneling, Least square fit

Language

English

Format

text

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