Single-Configuration Wavefunctions and Potential Curves for the Ground States of He2, Ne2, and Ar2

Potential energy curves are calculated for He2, Ne2, and Ar2 using single-configuration wavefunctions constructed from molecular orbitals. In one set of calculations the molecular orbitals are chosen to be linear combination of Hartree—Fock orbitals of the separated atoms (the LCAO-MO approximation). In another set of calculations SCF molecular orbitals are obtained by the expansion method (the SCF—MO approximation) with basis functions taken from SCF calculations on the separated atoms. SCF—MO's for He2 are also calculated with basis functions which have been ``optimized'' by varying the parameters in the exponents until the total energy is a minimum. Potential curves for these different calculations are compared among themselves and with experiment.