Predicted bismuth-tellurium under high pressures

The high-pressure structures of the Bi-Te system were theoretically predicted by this work, which also clarified some ambiguous structures. Using variable-composition evolutionary algorithms, the crystal structures of the Bi-Te system at high pressures were searched, and one new stable structure BiTe-P-1 was proposed. BiTe-P-1 was discovered to be the experiment's undetected structure by comparing with the experimental XRD. Thereafter, the pressure-composition diagram of the Bi-Te system was calculated using the first-principles method. In contrast to previous reports, Bi2Te3 only had two high-pressure structures, R-3m and C2/m, and it would decompose into BiTe and Te at 13.4 GPa. The calculation of quasi-harmonic approximation shown that the BCC alloy phase of Bi2Te3 only could exist stably under high temperature and high pressure. For BiTe, The phase transition route was P-3m1 -> P-1 -> Pm-3m, and the transition pressure was 7.5 and 11.2 GPa, respectively.