The structural stability and electronic states of GaSe monolayer with trigonal-antiprismatic (AP) structure, which is a recently discovered polymorph, were studied by first-principles calculations. The AP-phase GaSe monolayer was found stable, and the differences in energy and lattice constant were small when compared to those calculated for a GaSe monolayer with conventional trigonal-prismatic (P) structure which was found to be the ground state. Moreover, it was revealed that the relative stability of P-phase and AP-phase GaSe monolayers reverses under tensile strain. These calculation results provide insight into the formation mechanism of AP-phase GaSe monolayers in epitaxially grown GaSe thin films.

中文翻译：

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三角反棱结构单层GaSe的稳定性和电子结构的第一性原理研究

通过第一性原理计算研究了最近发现的多晶型物-三角反棱（AP）结构的GaSe单层的结构稳定性和电子态。发现与AP相的GaSe单层相比，它是稳定的，并且与针对具有传统三角棱柱（P）结构的GaSe单层（发现为基态）所计算出的能量和晶格常数的差异较小。此外，揭示了在拉伸应变下P相和AP相GaSe单层的相对稳定性反转。这些计算结果提供了外延生长的GaSe薄膜中AP相GaSe单层形成机理的见解。