Simple theoretical model for the van der Waals potential at intermediate distances. III. Anisotropic potentials of Ar--H/sub 2/, Kr--H/sub 2/, and Xe--H/sub 2/

Journal Article · Thu Jan 15 04:00:00 EST 1981 · J. Chem. Phys.; (United States)

OSTI ID:6668370

Tang, K T; Toennies, J P

A simple semiclassical theory of the van der Waals potential, which uses no empirical constants, was proposed and tested on atom--atom systems in an earlier paper (J. Chem. Phys. 66, 1496 (1977)). In a following paper (J. Chem. Phys. 68, 5501 (1978)) it was successfully applied to the prediction of the radial v/sub 0/(R) and anisotropic parts v/sub 2/(R) of the van der Waals potential expanded as V(R,..gamma..)=v/sub 0/(R)+v/sub 2/)R) x P/sub 2/(cos ..gamma..) (R is the distance between centers of mass and ..gamma.. is the angle between R and the molecular axis) of He--H/sub 2/ and Ne--H/sub 2/ for which all the necessary ab initio input data were available. In the present paper the method is applied to the heavier systems Ar--H/sub 2/, Kr--H/sub 2/, and Xe--H/sub 2/ for which the ab initio data are not available. The dispersion terms were estimated using the precise combining rule described in II. The anisotropic Born--Mayer parameters for the repulsive potentials were estimated by successive application of the Gilbert--Smith combining rules. The necessary input was the ab initio repulsive anisotropy in He--H/sub 2/ and the repulsive parameters for Ar--Ar, Kr--Kr, and Xe--Xe, which could be estimated from the experimental potential well parameters. The resulting Born--Mayer parameters were adjusted slightly to agree with the experimental v/sub 0/ potential parameters. The v/sub 2/ potentials predicted in this way are presented and compared with the best available experimental potentials of Le Roy and co-workers and Zandee and Reuss. Cross section anisotropy factors have also been calculated for direct comparison with the measured orientation dependence of integral cross sections measured by Reuss and co-workers. For all systems the agreement with experiment is very good and within the experimental error. Finally, a new law of corresponding states which predicts that the reduced shapes of the spherical symmetric and anisotropy potentials are identical is proposed.

• Research Organization: Max-Planck-Institut fuer Stroemungsforschung, 3400 Goettingen, Federal Republic of Germany
• OSTI ID: 6668370
• Journal Information: J. Chem. Phys.; (United States), Journal Name: J. Chem. Phys.; (United States) Vol. 74:2; ISSN JCPSA
• Country of Publication: United States
• Language: English

Related Subjects

640304* -- Atomic
Molecular & Chemical Physics-- Collision Phenomena
74 ATOMIC AND MOLECULAR PHYSICS
ANISOTROPY
ARGON
ATOM COLLISIONS
ATOM-MOLECULE COLLISIONS
COLLISIONS
ELEMENTS
FLUIDS
GASES
HYDROGEN
KRYPTON
MOLECULE COLLISIONS
NONMETALS
RARE GASES
SEMICLASSICAL APPROXIMATION
VAN DER WAALS FORCES
XENON