A study of molecular pair potentials A semiempirical approach

Journal Article · Thu Jan 01 04:00:00 EST 1976 · J. Chem. Phys., v. 64, no. 1, pp. 342-348

DOI:https://doi.org/10.1063/1.431927· OSTI ID:4085014

Ellis, R L

An expression is developed for the short range molecular pair potentials within the framework of the Heitler--London approach for molecules in a closed shell state. Assumptions common with the CNDO/2 semiempirical method are employed in evaluating the molecular integrals. The final expression depends only on quantities related to the atoms making up each molecule. There are four such quantities; (1) the atom charge density P/subm/; (2) the atom core charge Z/ subc//subm/; (3) the distance between atoms r/subm//subn/; and (4) the value of two electron repulsion integrals between atoms $gamma$/subm//subn/. In terms of these quantities the final expression has the simple form E$sup 1$a//subb/= (-1) $Sigma$/subm/(/suba//sup //sup Sigma/n/(/subb//sup /P/subm/P/subn/$gamma$/subm// subn/(Z/subc//subm//P/subm/+Z/subc//subn//P/subn/ -1)-Z/subc//subm/Z/subc//subn/ r$sup -1$/subm//subn/. Although several approximations are introduced to obtain this expression these are related to the evaluation of integrals, and no adjustable parameters are required for the evluation of E$sup 1$a//subb/. This potential is in good agreement with the results of ab initio calculations for the system He/H$sub 2$, Ne/H$sub 2$, and HF/HF. A comparison is also made with the results of the Gordon--Kim method for the system HF/HF. Both E$sup 1$a//subb/ and the Gordon--Kim method are found to give comparable results, but the method presented in this work is found to be computationally approx.3000 times faster per data point. (AIP)

• Research Organization: Department of Chemistry, University of Illinois, Urbana, Illinois 61801
• Sponsoring Organization: USDOE
• NSA Number: NSA-33-021151
• OSTI ID: 4085014
• Journal Information: J. Chem. Phys., v. 64, no. 1, pp. 342-348, Journal Name: J. Chem. Phys., v. 64, no. 1, pp. 342-348; ISSN JCPSA
• Country of Publication: United States
• Language: English

Related Subjects

*HELIUM-- INTERMOLECULAR FORCES
*HYDROGEN-- INTERMOLECULAR FORCES
640304* --Physics Research--Atomic
Molecular & Chemical Physics--Collision Phenomena
HEITLER-LONDON THEORY
N60400* --Physics (Atomic & Molecular)--Collision Phenomena