AgAlSe2晶体高压相变的第一性原理研究

First-principles Study on Phase Transition of AgAlSe2 Crystal at High Pressure

基于密度泛函理论,采用广义梯度近似法,研究了黄铜矿结构AgAlSe2在高压下的晶体结构、晶格动力学稳定性与电子结构。结果显示:在0 GPa时AgAlSe 2的晶格参数与实验值吻合,在13.9 GPa附近,质量密度、Se-Ag键长、Se-Al键长、晶格常数a突然增大,相对晶胞体积V/V0、晶格常数c突然减小,声子谱出现虚频,结构变得不稳定,带隙发生突变,数值呈减小趋势。表明AgAlSe2晶体在13.9 GPa附近发生结构相变。该研究为AgAlSe2晶体在理论上所能承受的高压提供信息支撑。

Based on the density functional theory,the structural,lattice dynamic stability and electronic properties of chalcopyrite AgAlSe2 under different pressures were investigated by generalized gradient approximation.The result show that,the lattice parameter of the chalcopyrite AgAlSe2 is consistent with the experimental values at 0 GPa,and the mass density,Se-Ag,Se-Al bond length and lattice constant a have a sudden increase,the relative cell volume V/V0 and lattice constant c suddenly decrease,and the phonon spectrum presents imaginary frequency,the structure becomes unstable,and the band gap changes abruptly,and the value shows a decreasing trend near 13.9 GPa.These results indicate that the chalcopyrite AgAlSe2 undergoes a structural phase transition near 13.9 GPa.This research provides information support for AgAlSe2 crystals under theoretically high pressure.