Metallization of CsI under pressure: Theoretical results

We report results of self-consistent, relativistic linear-muffin-tin-orbital calculations of the band structure of CsI under compression in the observed crystal structures. We show that the relativistic effects as well as the effects of the high-pressure structural phase transition—which have so far not been theoretically examined—reduce the metallization pressure significantly. We find that metallization occurs by the closure of the direct band gap at the Γ point. As the crystal is compressed the band gap closes faster in the tetragonal and orthorhombic phases than in the simple-cubic phase. Our calculated metallization volume, $V_M$/$V_0$=0.50, is in good agreement with recent experimental estimates.