Ab Initio Calculation of Vacancies and Interstitials in NiS₂

An ab initio plane-wave ultrasoft pseudopotential method based on the generalized gradient approximations has been utilized to investigate the electronic structure, atomic geometry, formation energy to provide a better understanding of properties of Ni disilicide. The vacancy and interstitial formation energies largely depend on the atomic chemical potentials. The formation energies of vacancies V_Si and V_Ni are in the range of 0.04--0.56 eV and 1.25--2.3eV, respectively and the formation energies of Si and Ni interstitials are 3.89--4.42 eV and 0.67--1.71 eV, respectively. The smaller Ni interstitial formation energy is in agreement with the experimental result that Ni interstitial atom is dominant diffusion species in NiSi₂