Theoretical analyses of phase transition and Debye-Waller factor of Si(111)-Ag√3x√3 surface

According to the recent STM measurements and first principles calculations, the ground state structure of Ag adsorbed Si(1 1 1) surface is the inequivalent triangle (IET) structure not but the honeycomb chained triangle (HCT) structure. A simplified theoretical model to describe the phase transition from HCT to IET is introduced. The interaction parameters in the model Hamiltonian are estimated from the first principles calculation based on the density functional theory, The properties related to the phase transition and the Debye-Waller (D-NV) factor are calculated with the Monte Carlo simulation, The calculated D-W factor takes the relatively large value corresponding to the thermal fluctuation of the surface Ag atoms and it qualitatively agrees with the experimental one. (C) 2001 Elsevier Science B.V, All rights reserved.