Using density functional theory, the crystal structure variation of AAuAl (A = Ca, Sc, and Ti) from orthorhombic Co₂Si-type to distorted hexagonal Fe₂P-type and then Ni₂In-type structures is shown to correlate with their electronic structures and valence electron counts, sizes of the active metals A, and site preferences for Au and Al atoms, which are arranged to maximize Au–Al nearest neighbor contacts. An evaluation of chemical pressure imposed by the varying A metals using total energy vs volume calculations indicates that larger unit cell volumes favor the orthorhombic structure, whereas smaller volumes favor the hexagonal structures. The electronic origin of the Mg₂Ga-type crystal structure of ScAuAl, refined as a distorted Fe₂P-type supercell doubled along the c-axis, indicates a Peierls-type distortion mechanism of the Au chains along the c-axis.

中文翻译：

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AAuAl（A = Ca，Sc和Ti）：Peierls变形，原子着色和结构竞争

使用密度泛函理论，表明AauAl（A = Ca，Sc和Ti）的晶体结构从正交Co ₂ Si型转变为扭曲的六角形Fe ₂ P型，然后是Ni ₂ In型结构与它们的相关性。电子结构和价电子数，活性金属A的大小以及Au和Al原子的位置偏爱，它们被安排成使Au-Al最近邻接触最大化。使用总能量与体积计算得出的变化的A金属施加的化学压力评估表明，较大的晶胞体积有利于正交晶系结构，而较小的体积则有利于六方晶结构。ScAuAl的Mg ₂ Ga型晶体结构的电子起源，精炼成扭曲的Fe_2个P型超级电池沿c轴加倍，表明Au链沿c轴的Peierls型变形机制。