Formation energy and electronic structure of silicon impurities in diamond

The formation energies and electronic structures of three kinds of Si impurities in diamond are studied using the modified neglect of differential overlap method and the discrete-variational local-density-functional method with cluster models. The results show that it is difficult for all of the silicon impurities (interstitial, substituting, and pair-interstitial) to be formed in diamond, and that there is local density of states within the band gap for the interstitial silicon and the pair interstitial, but not for the silicon substitution impurity in diamond. It is suggested that the silicon impurities in diamond destroy locally the sp³ hybrid of diamond, which results in changes in some intrinsic properties of diamond.