A Monte Carlo simulation study of H2 layers on NaCl(0 0 1)

Monte Carlo simulations show that, at one monolayer coverage, H2 molecules adsorbed on a NaCl(0 0 1) surface occupy all Na+ sites and form a commensurate c(2 × 2) structure. If the Cl− sites are occupied as well, a bi-layer p(2 × 1) structure forms. An examination of the H2 molecules’ rotational motion shows the molecular axes are azimuthally delocalized and so both of the structures acquire (1 × 1) symmetry in accord with experimental observations. These calculations also show that helicoptering o-H2 (J = 1, m = ±1) prefer to sit on top of Na+ sites, while cartwheeling o-H2 (J = 1, m = 0) prefers to locate over Cl− sites, in agreement with other work.