3-BODY CONTRIBUTION TO BINDING-ENERGY OF SOLID ARGON AND ANALYSIS OF CRYSTAL-STRUCTURE

The binding energy of solid argon has been computed using a symmetry-a dapted perturbation theory three-body potential. This energy equals -7 752.9 J/mol and agrees well with the experimental value of -7726 +/- 1 3 J/moI. The fee structure is favored over the hcp structure by 0.01%, in agreement with experimental observations. In accord with an early suggestion of Jansen [Adv. Quantum Chem. 2, 119 (1965)], inclusion of nonadditive exchange contributions were found to be necessary to under stand the preferred crystal structure and for accurate computation of the binding energy.