Atomic and electronic structure of the Si(111)-√3x√3-Ag surface reexamined using first-principles calculations

We have reexamined the atomic and electronic structures of the Si(111)-root 3x root 3-Ag surface using first-principles calculations within the local density functional approach. First, we found that a discrepancy among previous first-principles studies concerning the honeycombchained-triangle (HCT) model, which was believed to describe the structure of the surface, can be attributed to the difference in the structural parameters adopted in the calculations. Second, we have confirmed that the recently proposed inequivalent triangle (IET) model, where the positions of the Ag atoms are distorted a little from those in the HCT, is energetically more stable than the HCT one. We have also examined several other models that have distortions similar to the IET one. The results suggest that at room temperature the surface does not stay in the HCT configuration, but fluctuates between various configurations. (C) 2000 Elsevier Science Ltd. All rights reserved.