Zhang Jingyun, Yang Cuihong, Rao Weifeng, Hao Jian, Li Yinwei
Jiangsu Key Laboratory for Optoelectronic Detection of Atmosphere and Ocean, Nanjing University of Information Science & Technology, Nanjing, 210044, China.
Department of Physics, School of Physics & Optoelectronic Engineering, Nanjing University of Information Science & Technology, Nanjing, 210044, China.
Sci Rep. 2017 Oct 16;7(1):13251. doi: 10.1038/s41598-017-13610-x.
As the first known Weyl semimetals, binary compounds including TaP, TaAs, NbAs, and NbP have received worldwide interest. This work explored the phase behaviours of NbAs and NbP under high pressure up to 200 GPa via first-principles calculations combined with intelligent particle swarm optimization. Upon compression, a new phase of NbAs with P-6m2 symmetry appeared above 23 GPa and remained stable until 38 GPa, whereupon a monoclinic structure with space group P2 /c became more energetically favourable. This lasted until 73 GPa, when a Pm-3m phase followed. Surprisingly, NbP underwent a single phase transition around 63.5 GPa to a new phase with Cmcm symmetry that was completely distinct from the structures shown by TaAs-class compounds such as NbAs and TaAs. All these newly pressure-stabilized structures were dynamically stable at both high and ambient pressure. Electronic band structure calculations revealed a transition from semimetal to metal under high pressure. This work is meaningful and fundamental for future studies and applications of TaAs-class Weyl semimetals under compression or extreme conditions.
作为首批已知的外尔半金属，包括TaP、TaAs、NbAs和NbP在内的二元化合物受到了全球关注。这项工作通过结合智能粒子群优化的第一性原理计算，探索了NbAs和NbP在高达200 GPa的高压下的相行为。压缩时，一种具有P-6m2对称性的NbAs新相在23 GPa以上出现，并一直稳定到38 GPa，此时具有空间群P2 /c的单斜结构在能量上变得更有利。这种情况一直持续到73 GPa，之后是Pm-3m相。令人惊讶的是，NbP在63.5 GPa左右经历了一次单一的相变，变成了一种具有Cmcm对称性的新相，这与NbAs和TaAs等TaAs类化合物所呈现的结构完全不同。所有这些新的压力稳定结构在高压和常压下都是动态稳定的。电子能带结构计算表明，在高压下从半金属向金属转变。这项工作对于未来在压缩或极端条件下对TaAs类外尔半金属的研究和应用具有重要意义和基础性。
