Structure and energetics of van der Waals complexes of carbon monoxide with rare gases. He–CO and Ar–CO

Abstract

The potential energy surfaces for Ar–CO and He–CO were calculated at the fourth order Mo/ller–Plesset perturbation theory and analyzed using perturbation theory of intermolecular forces. Both the complexes reveal only one minimum related to the approximately T-shaped geometry. For Ar–CO, our best ab initio estimates of Re and De are 3.70 Å and 496 μhartrees, respectively, and the optimal angle Rg–com–O is about 80°. For He–CO, our best Re and De are 3.4 Å and 100 μhartrees, respectively, at the optimal angle Rg–com–O of 70°. Our geometrical parameters agree very well with the experimental data. Our ab initio well depths are estimated to be within ±5% in error and are expected to be the most accurate in the literature so far. The De values were obtained with extended basis sets which included bond functions. Basis set effects on the dispersion and electrostatic correlation terms that are caused by bond functions were also analyzed. Both complexes are bound by dispersion forces, but the anisotropy of the interaction is determined by the exchange repulsion component. This anisotropy may be interpreted in terms of the relative concentrations and depletions in the diffuse region of the CO charge density. The electrostatic and induction effects proved to be negligible.

State to state He–CO rotationally inelastic scattering

“…[12][13][14] Thachuk et al 1 and Dham and Meath 15 subsequently tested the different potentials' predictions against several experimental observables and found that the XC͑fit͒ potential was at least as good as the others.…”

Ro-vibrational quenching of CO (v = 1) by He impact in a broad range of temperatures: A benchmark study using mixed quantum/classical inelastic scattering theory

“…[9][10][11][12]28 The improvement of detection techniques 29,30 and development of the PES [31][32][33] went through several refinement cycles. Finally, an acceptable agreement between theory and experiment has been reached in different parts of the desired broad range of temperatures.…”

Rovibrational structure of the Ar–CO complex based on a novel three-dimensional ab initio potential

“…The Ar-CO complex can be considered a prototype van der Waals system, as witnessed by the extensive experimental [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19] and theoretical [20][21][22][23][24][25][26][27][28][29][30][31] work on its description. For example, the first paper, published in 1978 by Parker and Pack, 20 used Ar-CO as a model system for the development of electron gas methods for calculating intermolecular potential energy surfaces ͑IPESs͒.…”