Refined ab initio intermolecular ground-state potential energy surface for the He-C<sub>2</sub>H<sub>2</sub> van der Waals complex - Danish National Research Database-Den Danske Forskningsdatabase

^{1} Department of Applied Mathematics and Computer Science, Technical University of Denmark^{2} Mathematics, Department of Applied Mathematics and Computer Science, Technical University of Denmark^{3} University of Santiago de Compostela^{4} Utah State University

DOI:

10.1080/00268976.2013.793837

Abstract:

A refined CCSD(T) intermolecular potential energy surface is developed for the He-C2H2 van der Waals complex. For this, 206 points on the intermolecular potential energy surface, evaluated using the CCSD(T) method and the aug-cc-pVQZ basis set extended with a set of 3s3p2d1f1g midbond functions, are fitted to a 15-parameter analytic function. The potential is characterised by minima of-24.21 cm-1 at distances between the rare gas atom and the C2H2 centre of mass of 4.3453 Å, and with the complex in a linear configuration. At intermediate distances the surface is rather similar to that developed previously by Munteanu and Fernández (J. Chem. Phys., 123, 014309, 2005) but differs notably at short range. The improved potential energy surface should, therefore, be particularly useful for computations of collision line broadening. Dynamical calculations of a number of rovibrational bound state energies and wave functions are presented. Inspection of the nodal surfaces of several low lying excited states shows that the complex is close to the free rotor limit.

Type:

Journal article

Language:

English

Published in:

Molecular Physics, 2013, Vol 111, Issue 9-11, p. 1173-1177

Keywords:

Calculations; Potential energy surfaces; Van der Waals forces; Quantum chemistry