Path Integral Monte Carlo Simulations of H2 Surfaces

by Marcus Wagner and David M. Ceperley, NCSA Applications Group

The (1,1,1)-surfaces of bulk solid molecular hydrogen have been studied at temperatures between 0.5K and 1.3K, 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. Density profiles parallel and perpendicular to the free H2 surface, total energies, and surface tension are computed. 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.