Abstract
We study the adatom system on (111) surface of diamond crystal structure. As a model of the adatom system, we consider two-dimensional hexagonal lattice gas model with excluded volume restriction among adatoms sitting on T_4 sites and H_3 sites. We calculate thermodynamical quantities of the lattice gas models in disordered phase by product-wave-function renormalization group (PWFRG) method. We apply the results to Si (111) surface.
