压力下氮化铝相转变及结构性质的第一性原理研究

Pressure-induced phase transitions and structure properties of AlN by first-principles studies

利用密度泛函理论(DFT)研究了AlN的六角纤锌矿结构(B4),岩盐矿结构(B1),过渡态中间相六方结构(Hexa)和过渡态中间相四方结构(Tetra),计算了AlN在不同压力下B4和B1结构和过渡态中间相六方结构和四方结构的焓值,计算发现B4和B1相的转变压力是17.27 GPa,低压区中间相六方结构稳定,高压区中间相四方结构更稳定,AlN的常见的B4结构是直接带隙结构,带隙宽度是4.095 eV,带隙宽度与外压力之间关系符合二次函数方程,与其它理论研究结果一致.

This paper reports a theoretical study for the wurtzite phase(B4),rocksalt phase(B1)and transition intermediate phases hexagonal structure(Hexa)and tetragonal structure(Tetra)of AlN.Enthalpies of the different phases of AlN under different hydrostatic pressures have been calculated from the density functional theory(DFT).The transition pressure is obtained from the enthalpy curve crossings and determined to be 17.27 GPa between the B1 and B4 phases of AlN.The intermediate hexagonal structure is more stable at low pressure and the intermediate tetragonal structure remains more stable at high pressure.Our results show that the wurtzite phase(B4)is of direct bandgap(4.095 eV).The bandgap energy as a function of applied pressure fits a second-order polynomial and these values are in good agreement with the earlier first-principles calculations.