Path integral monte carlo simulations of H₂ surfaces

The (1,1, 1)-surfaces of bulk solid molecular hydrogen have been studied at temperatures between 0.5 K and 1.3 K, using path integral Monte Carlo. A general method is introduced for constructing an external potential to represent the tail correction for an arbitrary heterogeneous layered bulk substrate-adsorbate system. We compute density profiles parallel and perpendicular to the free H₂ surface, total energies, and the surface tension. The structure of partial (not completely filled) surface layers is investigated and found liquid for some filling fractions. Quantum exchange of H₂ molecules at the free surface is observed and the possibility of superfluidity in a surface layer of H₂ is discussed.