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.
