Abstract
A new c(4×2) structure for the Si(100) surface is proposed in which the second-layer atoms are dimerized and the top-layer atoms form π-bonded chains. Pseudopotential total-energy calculations indicate that this c(4×2) dime-plus-chain structure has a lower energy’than the (2×1) dimerized surface. The bond topology of the structure explains the streaking and weakness of the (1/4)-order diffraction spots observed in low-energy electron and He-atom diffraction.