Si(111):Na: Structural and electronic properties from ab initio molecular dynamics

We present an ab initio molecular-dynamics (Car-Parrinello) study of Na adsorption on Si(111). For one-monolayer coverage the bulk-terminated surface does not reconstruct, in agreement with recent low-energy-electron-diffraction data. The equilibrium Na geometry largely confirms Northrups predictions with an albeit partially ionic bonding. Energy bands are in excellent agreement with angle-resolved photoemission. Temperature effects and metastable configurations on the 1×1 and 2×1 phases are discussed. For half-monolayer coverage, the 1×1 structure is predicted to be unstable. © 1992 The American Physical Society.