State Key Laboratory of Superhard Materials, College of Physics, Jilin University, Changchun 130012, People's Republic of China.
J Phys Condens Matter. 2010 Jun 9;22(22):225401. doi: 10.1088/0953-8984/22/22/225401. Epub 2010 May 12.
Pressure-induced phase transitions of BaH₂ have been studied by ab initio calculations. Our results show that BaH₂ transforms from the cotunnite structure to the InNi₂-type structure at about 2.3 GPa, which is in agreement with experimental results. The InNi₂ phase is predicted to be an insulator and transforms to a metallic phase with an AlB₂-type structure at about 34 GPa. Under higher pressure, a post-AlB₂ phase with the YbZn₂-type structure (space group Imma, 4 f.u./cell) is predicted, which is both dynamically and mechanically stable. Analysis of the enthalpies for both AlB₂ and YbZn₂ phases further supports the existence of this new phase. The [AlB₂ → YbZn₂] structural phase transition is identified as a second-order nature, driven by the softening of the transverse acoustic phonon mode at the L point (0.5, 0.0, 0.5).
通过第一性原理计算研究了 BaH₂ 的压力诱导相变。我们的结果表明，BaH₂ 在约 2.3 GPa 时从 cotunnite 结构转变为 InNi₂ 型结构，这与实验结果一致。预测 InNi₂ 相为绝缘体，并在约 34 GPa 时转变为具有 AlB₂ 型结构的金属相。在更高的压力下，预测存在具有 YbZn₂ 型结构（空间群 Imma，4 f.u./cell）的后 AlB₂ 相，该相在动力学和力学上都是稳定的。对 AlB₂ 和 YbZn₂ 相的焓分析进一步支持了这种新相的存在。[AlB₂→YbZn₂]结构相变被确定为二阶性质，由 L 点（0.5，0.0，0.5）处横声学声子模式软化驱动。
