Wang Wenjie, Zhang Chuanzhao, Jin Yuanyuan, Li Song, Zhang Weibin, Kong Panlong, Xie Chengwu, Du Chengzhuo, Liu Qian, Zhang Caihong
Department of Physics and Optoelectronic Engineering, Yangtze University, Jingzhou, 434023, China.
School of Physical Science and Technology, Key Laboratory of Advanced Technologies of Materials, Southwest Jiaotong University, Chengdu, 610031, China.
Sci Rep. 2020 Jun 1;10(1):8868. doi: 10.1038/s41598-020-65910-4.
Based on a combination of the CALYPSO method for crystal structure prediction and first-principles calculations, we explore the crystal structures of VH under the pressure range of 0-300 GPa. The cubic Fm-3m phase with regular VH cubes is predicted to transform into orthorhombic Pnma structure with fascinating distorted VH tetrakaidecahedrons at 47.36 GPa. Both the Fm-3m phase at 0 GPa and the Pnma phase at 100 GPa are mechanically and dynamically stable, as verified with the calculations of elastic constants and phonon dispersions, respectively. Moreover, the calculated electronic band structure and density of states indicate both stable phases are metallic. Remarkably, the analyses of the Poisson's ratio, electron localization function (ELF) and Bader charge substantiate that both stable phases are ionic crystals on account of effective charges transferring from V atom to H. On the basis of the microscopic hardness model, the Fm-3m and Pnma crystals of VH are potentially incompressible and hard materials with the hardness values of 17.83 and 17.68 GPa, respectively.
基于晶体结构预测的CALYPSO方法与第一性原理计算相结合，我们探索了VH在0 - 300 GPa压力范围内的晶体结构。预测具有规则VH立方体的立方Fm-3m相在47.36 GPa时转变为具有迷人扭曲VH十四面体的正交Pnma结构。分别通过弹性常数和声子色散计算验证，0 GPa时的Fm-3m相和100 GPa时的Pnma相在力学和动力学上都是稳定的。此外，计算得到的电子能带结构和态密度表明这两个稳定相都是金属性的。值得注意的是，泊松比、电子定域函数（ELF）和巴德电荷分析证实，由于有效电荷从V原子转移到H，这两个稳定相都是离子晶体。基于微观硬度模型，VH的Fm-3m和Pnma晶体分别具有17.83和17.68 GPa的硬度值，是潜在的不可压缩和硬质材料。
