To explore the stable crystal structure and structural evolution of aluminum monoxide (AlO), we predict four novel structures and investigate their stability, mechanical, electronic and Raman properties using particle-swarm optimization (PSO) technique and density functional theory (DFT) calculations. Depending on the symmetry and bonding characteristics, these novel structures exhibit various stability and properties under pressure. The oP-AlO (space group Imm2) is the most stable structure under ambient pressure, while the h-AlO (space group R$\overline{3}$$\overline{3}$m) structure becomes the most stable above 3 GPa and remains so up to 100 GPa. The h-AlO structure stands out due to distinct bonding interactions at different Wyckoff positions of aluminum atoms, particularly the rhombus arrangement formed by Al-II atoms, which gives rise to a Dirac cone in its electronic structure that is insensitive to pressure. In contrast, the m-AlO (space group C2/m), oP-AlO and oD-AlO (space group I/mmm) structures undergo first-order phase transitions, accompanied by significant structural changes and discontinuities in Al-O bonds. The oP-AlO and oD-AlO structures, in particular, exhibit unstable transformations during these transitions. Additionally, the vibrational characteristics of predicted structures are discussed, and the significant differences facilitate future experimental identification through Raman spectroscopy.

中文翻译：

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预测的一氧化铝相及其在压力下的结构演变


为了探索一氧化铝 （AlO） 的稳定晶体结构和结构演变，我们预测了四种新结构，并使用粒子群优化 （PSO） 技术和密度泛函理论 （DFT） 计算研究了它们的稳定性、力学、电子和拉曼特性。根据对称性和键合特性，这些新颖的结构在压力下表现出不同的稳定性和特性。oP-AlO（空间群 Imm2）在环境压力下是最稳定的结构，而 h-AlO（空间群 R $\overline{3}$ m）结构在 3 GPa 以上最稳定，并在 100 GPa 之前保持最稳定。h-AlO 结构之所以突出，是因为在铝原子的不同 Wyckoff 位置存在不同的键合相互作用，特别是 Al-II 原子形成的菱形排列，这在其电子结构中产生了对压力不敏感的狄拉克锥。相比之下，m-AlO （空间群 C2/m）、oP-AlO 和 oD-AlO （空间群 I/mmm） 结构经历一阶相变，伴随着 Al-O 键的显着结构变化和不连续性。特别是 oP-AlO 和 oD-AlO 结构在这些转变过程中表现出不稳定的转变。此外，还讨论了预测结构的振动特性，并且显着差异有助于未来通过拉曼光谱进行实验鉴定。