Electronic structure of Sb/sub 2/Te/sub 3/ under pressure

Recent experimental data indicate that thermoelectric properties of alloys commonly used in room-temperature cooling devices, Sb/sub 2/Te/sub 3/ and Bi/sub 2/Te/sub 3/, improve significantly under pressure. Here we analyze the structure and the electronic properties of Sb/sub 2/Te/sub 3/ under pressure within the framework of density functional theory using the relativistic version of the full potential linearized augmented plane wave (FP-LAPW) method. We use an approach that does not require any external input. First, we calculate the crystallographic parameters as a function of pressure and show that the results are in reasonable agreement with the available experimental data. Then, we calculate the electronic band structure of the material under pressure and discuss its properties. It is shown that the band gap of Sb/sub 2/Te/sub 3/ reduces under pressure and closes completely at about 2 GPa. This is consistent with the experimental data on the resistivity. Other details of the pressure dependence of the band structure are also discussed.