Structural and electrical properties of Ga–Te systems under high pressure*

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.

Prediction of scandium tetraboride from first-principles calculations: Crystal structures, phase stability, mechanical properties, and hardness*

“…[35] The details of convergence tests have been described elsewhere. [36][37][38] 2 presents the formation enthalpy of six phases as a feature of pressure for ScB 4 , and it can be clearly seen that the predicted Cmcm structure is energetically more favorable than the other structures at ambient pressure. As the pressure increases, the Pnma phase becomes the most stable when the pressure is higher than about 18 GPa.…”

Boron at tera-Pascal pressures

“…Here, we used the ab initio evolutionary algorithm USPEX, [18][19][20][21][22][23][24] which can simultaneously find crystal structures of all stable elemental crystals in multi-pressures. In our searches at 500 GPa, 1500 GPa, 2000 GPa, and 5000 GPa pressure points, the initial population included 120 structures with up to 28 atoms per primitive cell, with all subsequent generations consisting of 50 structures produced by heredity (30%), transmutation (20%), soft mutation (20%), and a random symmetric generator (30%).…”

Chemical bonding within AIIIBVI materials under uniaxial compression

“…21,23 For GaTe, the transition to the rocksalt phase is expected at a pressure of about 7 GPa. 24 However, it is important to note that low-angle XRD, which is commonly used to study two-dimensional materials, can be insensitive to local distortions and can sometimes lead to erroneous conclusions. 25 Furthermore, XRD and X-ray absorption fine structure (XAFS) cannot provide information about the nature of chemical bonding.…”