EXPLICITLY CORRELATED GAUSSIAN FUNCTIONS IN VARIATIONAL CALCULATIONS - THE GROUND-STATE OF HELIUM DIMER

An explicitly correlated wave function is applied to variationally sol ve the Schrodinger equation within the Born-Oppenheimer approximation for the ground state of the helium dimer. The total electronic energy E as a function of the internuclear distance R is calculated for a wid e range of R. An upper bound to the interaction energy curve is also p resented. High accuracy of these calculations enables a derivative fun ction dE/dR to be computed. At the equilibrium distance of 5.6 bohr th e electronic energy is -5.807 483 422 E-h and the upper bound to the i nteraction energy equals -10.95 K. To date, this is the most accurate variational total electronic energy curve of a four electron system.