Equation of state of solid He-3

We present results of diffusion Monte Carlo calculations for the bcc and hc p phases of solid He-3, using a recent ab initio interatomic potential, inc luding two- and three-body terms. This potential is found to yield an equat ion of state fur condensed He-4 in excellent agreement with experiment, in a wide density range. For He-3, we find a systematic discrepancy, worth 0.7 K, between our computed equation of state and a commonly accepted experime ntal one. We attribute such a discrepancy to an importance choice of refere nce energy in the determination of the experimental equation of state.