PRESSURE INDUCED STRUCTURAL PHASE TRANSITION AND SUPERCONDUCTIVITY IN TITANIUM METAL

The electronic band structure, density of states, structural phase transition, and superconducting transition temperature under normal and high pressures are reported for titanium (Ti). The normal pressure band structure and density of states of hcp-Ti agree well with the previous calculations. The high pressure band structure exhibits significant deviations from the normal pressure band structure due to s, p -> d transition. On the basis of band structure and total energy results obtained using full potential linear muffin-tin orbital method ( FP LMTO), we predict a phase transformation sequence of alpha (hcp) -> omega (hexagonal) -> gamma (distorted hcp) -> beta (bcc) in titanium under pressure. From our analysis we predict a delta ( distorted bcc) phase which is not stable at any high pressures. According to the present calculation, at normal pressure, the superconducting transition of hcp-Ti occurs at 0.36K which is in agreement with the experimental observation of 0.4 K. When the pressure is increased, it is predicted that, T-c increases at a rate of 3.123K/Mbar in hcp-Ti. On further increase of pressure T-c begins to decrease at a rate of 1.464 K/Mbar.