Semiconductor–metal transition of pyriteFeS2 under high pressure by full-potential linearized-augmented plane wave calculations

Abstract

The effects of hydrostatic pressure on the electronic band structure of the semiconductor mineral ironpyrite FeS2 have been investigated theoretically by an ab initio full-potential linearized-augmented planewave (FPLAPW) method within a local approximation (LDA/GGA) to the density functionaltheory. The calculations predict that at a pressure of 94.1 GPa the indirect band gap of pyriteFeS2 vanishes and the material becomes a metal. This is due to the presence of the S–S and Fe–Sbonds, which provide novel energy band distortions in the process of attaining the metallicstate. Analysis indicates that, under increasing high pressure, the conduction bands(3pz ofsulfur and 3dx2−y2+3dxy of iron) intrude downwards into the valence bands, which are predominantly 3d in nature.At normal pressure, the lattice constant, the bulk modulus, sulfur position parameteru, S–S bond length, and the indirect band gap of pyriteFeS2 are calculated using a fully relaxed unit cell and found to be equal to 541.8 pm, 159.7 GPa,u = 0.383, 219.5 pm and 0.45 eV, respectively. Apart from the gap, which is too small (the usual ‘LDAerror’), these results agree well with recent experiments. The effective masses of an electronat selected points in the conduction band are reported.