One-step first principles molecular-dynamics (FPMD) simulations were carried out to investigate structural transformations in wurtzite-type AlN under compression and decompression. The hexagonal transformation path $P{6}_{3}mc\text{−}P{6}_3/mmc\text{−}Cmmm\text{−}Fm\overline{3}m$ was identified during compression at $P=50$ GPa and $T=500$ K. The inversion of this path of transformation was established at the decompression of compressed rock-salt AlN at 1500 K. The plausible origin of these transformations is established. The occurrence of intermediate and metastable phases was predicted by taking into account their dynamical and elastic instability, and for this purpose, phonon spectra and elastic constant calculations were performed. FPMD simulations were used to generate amorphous AlN and to investigate its behavior under pressure. The sequence of phase transitions: low-density amorphous—high-density amorphous—rock-salt type was revealed at $P=40$ GPa, and the thermodynamic and mechanical properties of crystalline and amorphous AlN were compared. It was found that the one-step FPMD simulations is a viable scheme to predict phase transitions in crystalline and amorphous AlN with higher precision compared with other FPMD approaches with step-wise pressure changes.

中文翻译：

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第一性原理研究晶体和非晶态AlN的压力诱导相变和性质

一步一步的第一原理分子动力学（FPMD）模拟进行了研究在压缩和减压下纤锌矿型AlN的结构转变。六角形转换路径$P{6}_3米C\text{-}P{6}_3/米米C\text{-}C米米米\text{-}F米\overline{3}米$ 在压缩期间被确定为 $P=50$ GPa和 $Ť=500$ K.在1500 K下压缩岩石盐AlN的减压过程中，确定了该转变路径的反演。确定了这些转变的合理起源。考虑到中间相和亚稳相的动力学和弹性不稳定性，可以预测它们的发生，为此，进行了声子谱和弹性常数的计算。FPMD模拟用于生成非晶态AlN并研究其在压力下的行为。相变的顺序为：低密度非晶态-高密度非晶态-岩盐型揭示于$P=40$ 比较了GPa以及晶体和非晶AlN的热力学和机械性能。已发现，与其他具有逐步压力变化的FPMD方法相比，单步FPMD模拟是一种可行的方案，可以以更高的精度预测晶体和非晶AlN中的相变。