Variational Calculations on LiquidHe4andHe3

Assuming a Lennard-Jones 6-12 potential with the de Boer—Michels parameters, the ground-state energies of systems of liquid ${\mathrm{He}}^4$ and ${\mathrm{He}}^3$ are calculated by a variational procedure in conjunction with the method of correlated basis functions. Comparisons are made with the results of McMillan and of Schiff and Verlet. These comparisons shed some light on the validity and adequacy of the Jastrow- and Jastrow-Slater—type wave functions in the description of helium liquids.