THEORETICAL CALCULATIONS FOR SI(001)-(2X1)CL

We have investigated the atomic geometry, electronic states and bondin g at the Si(001)-(2 x 1) surface covered with a monolayer of Cl. The c alculations were performed with ab initio pseudopotentials, using a pl ane wave basis and the local density approximation. We find that the a dsorption of Cl results in an elongated symmetric Si dimer. The calcul ated Si-Cl, Si-Si (dimer) and Si-Si (back-bond) distances are 2.08 Ang strom, 2.43 Angstrom and 2.34 Angstrom, respectively. The Si-Cl bond i s inclined at 20 degrees with respect to the surface normal. Our resul ts for atomic geometry and electronic states are in good agreement wit h available experimental data. (C) 1998 Elsevier Science B.V. All righ ts reserved.