COMPUTER-SIMULATIONS OF BENZENE ADSORBED ON GRAPHITE .1. 85-K

Computer simulations of the structure and energy of benzene layers adsorbed on graphite at 85 K are presented. Models for the benzene-benzene and the benzene-solid interaction potentials are developed. These give a stable square-root 7 x square-root 7 commensurate film, in agreement with experiment. It is shown that the orientations of these adsorbed molecules are not entirely parallel to the surface as generally assumed. The fraction of nonparallel molecules in the monolayer is small but increases with increasing coverage. The bilayer film is also studied; this film has somewhat less stabilization energy than the bulk crystal, but does not transform into the bulk during the duration of the simulation. Also, the second layer is orientationally less well ordered than the first. Comparisons with available experimental data are made.