Structural and electronic structure properties of FeSi: the driving force behind the stability of the B20 phase

We present the results of a first-principles pseudopotential plane-wave stu dy for the structural properties of the epsilon -FeSi (B20), NaCl (B1) and CsCl (B2) structures of FeSi. The calculations were performed using the loc al density and the generalized gradient approximations (LDA and GGA), for t he exchange-correlation potential. The electronic structures of the B1 and B2 phases have been similarly investigated. These calculations have enabled us to identity the driving force behind the crystallization of FeSi in the B20 phase. Both the B1 and B2 phases are found to be semimetallic, with th e Fermi energy lying in a pseudo-band-gap. The B20 structure is predicted t o become unstable with respect to the B2 phase at a moderate pressure, of 1 3.5 and 10.9 GPa according to the GGA and LDA calculations, respectively.