Diffusion Monte Carlo study of the equation of state of solid para-H-2

The diffusion Monte Carlo method is used to exactly solve the N-body Schroedinger equation for a system of para-H-2 molecules at different densities described as pointlike particles interacting via an effective potential. We compare the results obtained using two of the most used model interactions, i.e., the Silvera-Goldman and the Buck potentials in order to assess their validity. We also discuss the role of explicit three-body forces by adding a term of the Axilrod-Teller kind. This term corrects the large underestimation of the pressure given by the standard two-body interactions commonly employed.