Interatomic potential for the condensed phases of helium atoms

Results from diffusion Monte Carlo have been used in fits of a damping function of the triple dipole and of the intensity of the exchange three-body interactions. The equations of state obtained considering this three-body potential are in excellent agreement with experiment both at the solid and liquid phases. The calculations show that exchange nonadditivities that contribute less than 0.2% of the two-body potential energy in the solid phase are needed to describe the properties of a system of helium atoms.

Figure 1

Ground-state energies as a function of the density. Energy values for the liquid phase are displayed in the left side of the frame. The dashed line represents a fit of DMC results in the liquid phase. The experimental data of Ref. 32 are shown as circles. The right side of the frame show energies corresponding to the solid phase. A fit of the results for the ground-state energies in the solid phase is represented by the solid line. The squares stand for the experimental data of Ref. 31.