Molecular-dynamics simulation has been employed to investigate a previously proposed statistical-mechanical model [F. H. Stillinger, Phys. Rev. B 46, 9590 (1992)] for dimer buckling on the reconstructed Si(001) surface. Using model parameters suggested by low-temperature scanning-tunneling-microscopy observations, the calculations reveal a weakly first-order phase transition from a low-temperature c(4×2) pattern of buckled dimers, to a disordered high-temperature phase in which dimers have the untipped state as their most probable configuration. Alterations of input parameters establish that the thermal behavior of the generic model is sensitive to their specific values. Cases of strong first-order and of higher-order (Ising-like) phase transitions have also been simulated, as well as a case devoid of transitions.

• Received 28 June 1993

DOI:https://doi.org/10.1103/PhysRevB.48.15047