Structural and electrical properties of Ga–Te systems under high pressure**Project supported by the National Key R&D Program of China (Grant Nos. 2018YFA0305900 and 2016YFB0201204), the National Natural Science Foundation of China (Grant Nos. 51632002, 51572108, 11574109, 91745203, and 11634004), Program for Changjiang Scholars and Innovative Research Team in University, China (Grant No. IRT_15R23), and National Fund for Fostering Talents of

Abstract

First-principles evolutionary calculation was performed to search for all probable stable Ga–Te compounds at extreme pressure. In addition to the well-known structures of P63/mmc and Fm-3m GaTe and I4/m Ga2Te5, several new structures were uncovered at high pressure, namely, orthorhombic I4/mmm GaTe2 and monoclinic C2/m GaTe3, and all the Ga–Te structures stabilize up to a maximum pressure of 80 GPa. The calculation of the electronic energy band indicated that the high-pressure phases of the Ga–Te system are metallic, whereas the low-pressure phases are semiconductors. The electronic localization functions (ELFs) of the Ga–Te system were also calculated to explore the bond characteristics. The results showed that a covalent bond is formed at low pressure, however, this bond disappears at high pressure, and an ionic bond is formed at extreme pressure.