GaN相变及热力学性质的理论研究

利用基于密度泛函理论的第一原理方法研究了GaN的纤锌矿、闪锌矿、氯化钠三种结构的结构性质以及高压下GaN的相变.利用焓相等原理得出GaN从闪锌矿结构到氯化钠结构的相变压强约为41.9GPa,与实验值和他人理论计算值相符合.通过准谐德拜模型得到了GaN的闪锌矿和氯化钠两种结构不同温度下热膨胀系数与压强的关系,不同温度下体积与压强的关系以及不同压强下热容与温度的关系.

Theoretical study on phase transformation and thermodynamic properties of GaN

Using the first-principles method based on density functional theory, we have studied the structural properties of GaN with wurtzite, zinc-blende and rocksalt structures and the phase transition of GaN under high pressure. According to the isoenthalpy principle, the phase transition pressure from zinc-blende structure to rocksalt structure of GaN is about 41.9GPa, which is consistent with the experimental results and other theoretical results. Employing the quasi-harmonic Debye mode, we have calculated the relationships between the thermal expansion coefficient and the pressure of GaN with zinc-blende structure and rocksalt structure at different temperatures. The relationships between the volume and pressure at different temperatures, and those between the heat capacity and temperature under different pressures are also obtained.