Low-temperature phase diagram of condensedpara-hydrogen in two dimensions

Extensive Path Integral Monte Carlo simulations of condensed para-hydrogen in two dimensions at low temperature have been carried out. In the zero temperature limit, the system is a crystal at equilibrium, with a triangular lattice structure. No metastable liquid phase is observed, as the system remains a solid down to the spinodal density, and breaks down into solid clusters at lower densities. The equilibrium crystal is found to melt at a temperature close to 70.3em0exK.