Allotropes of tellurium from first-principles crystal structure prediction calculations under pressure.

We investigated the allotropes of tellurium under hydrostatic pressure based on density functional theory calculations and crystal structure prediction methodology. Our calculated enthalpy-pressure and energy-volume curves unveil the transition sequence from the trigonal semiconducting phase, represented by the space group P 3 1 21 in the range of 0-6 GPa, to the body centered cubic structure, space group Im 3̄ m , stable at 28 GPa. In between, the calculations suggest a monoclinic structure, represented by the space group C 2/ m and stable at 6 GPa, and the β-Po type structure, space group R 3̄ m , stable at 10 GPa. The face-centered structure is found at pressure as high as 200 GPa. As the pressure is increased, the transition from the semiconducting phase to metallic phases is observed.