Phase Stability and Elastic Properties of оne Dimensional Long Period Structures of Al₃Ti under High Pressure

E-ISSN： 1662-9752|2016|850|354-361

ISSN： 0255-5476

Source： Materials Science Forum, Vol.2016, Iss.850, 2016-04, pp. : 354-361

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Abstract

Phase stability and elastic properties of seven one dimensional long period structures (1D-LPSs) of Al₃Ti under high pressure have been systematically investigated by first-principles calculations. The enthalpy differences indicate that Al₃Ti will undergo a phase transition from 1D-LPSs to L1₂ structure at high pressure. With increase of antiphase boundary period parameter M’, the enthalpy initially decreases and then increases, and the enthalpy for D0₂₃ is the smallest. Oppositely, the phase transition pressure firstly increases and then decreases, and the maximum is for D0₂₃. The elastic constants and elastic moduli B, G and E increase monotonically with increase of pressure, and the corresponding second-order polynomial fits are also obtained. Interestingly, the pressure dependence of Poisson’s ratio show similar tendency with that of B/G ratio. Both the B/G ratios and the Cauchy pressures reveal that these 1D-LPSs exhibit brittleness at high pressure.