Ab initio study of electronic properties of CoSi_2 and NiSi_2 in the fluorite structure

摘要

The lattice structure and electronic properties of perfect CoSi_2 and NiSi_2 have calculated using an ab initio plane-wave ultrasoft pseudopotential method based on the generalized gradient approximations (GGA). Special attention is paid to the formation energies of the vacancy, which largely depend on the atomic chemical potentials of Si and metal atom: in Si-rich limit, the formation energies of Si and Co vacancies are 2.39 eV and 0.56 eV whilst those are 1.53 eV and 2.29 eV in Co-rich limit in CoSi_2, respectively. For NiSi_2, the formation energies of Si and Ni vacancies are 0.56 eV and 1.25 eV in Si-rich limit and those are 0.04 eV and 2.3 eV in Ni-rich limit.