AN AB-INITIO HARTREE-FOCK STUDY OF THE B/SI(001)2X1 ADSORPTION SYSTEM

The adsorption of boron onto the Si(001)2 x 1 surface is studied at 0.5 monolayer (ML) coverage using the linear combination of atomic orbitals (LCAO) pseudopotential Hartree-Fock method for periodic systems embodied in the CRYSTAL program. Four stable structures are determined within a range of 0.13 Hartree/(2 x 2 surface unit cell). The minimum energy configuration is an ad-dimer on-top configuration in which the B dimers are oriented parallel to the adjacent Si dimers. The only stable structure exhibiting a 2 x 1 surface periodicity is one in which the boron lies just below the surface. These results are compared with ab initio Hartree-Fock cluster calculations and with experimental data.