Cheng Hao, Mao Ai-Jie, Cheng Xiao-Rong, Tian Hao, Dou Xi-Long, Yang Si-Min, Kuang Xiao-Yu
Institute of Atomic and Molecular Physics, Sichuan University, Chengdu 610065, People's Republic of China.
J Phys Condens Matter. 2019 Dec 18;31(50):505406. doi: 10.1088/1361-648X/ab420d.
We perform the first-principles calculations combined with the particle swarm optimization algorithm to investigate the high-pressure phase diagrams of Na[Formula: see text]F ([Formula: see text] = Mn, Ni, Zn). Two reconstructive phase transitions are predicted from Pv-[Formula: see text] to pPv-[Formula: see text] at about 9 GPa and pPv-[Formula: see text] to ppPv-[Formula: see text] at around 26 GPa for NaZnF. That is not the case for NaMnF-a direct transition (reconstructive transition in nature but with the same Pnma space group) from Pv-[Formula: see text] to ppPv-[Formula: see text] phase around 12 GPa. Strikingly, our simulated results manifest that a disproportionation phase of NaZnF post-perovskite is uncovered along the way, which provides a successful explanation for the observed results in experiment. Additionally, the mechanical and thermal properties, especially the dynamical property, of the four NaZnF phases have also been studied. Here, we reveal the obvious softening of [Formula: see text]-wave velocity and bulk sound speed in pPv-[Formula: see text]-to-ppPv-[Formula: see text] transition, which may result in the discontinuity of seismic waves propagation through the Earth's interior.
我们结合粒子群优化算法进行第一性原理计算，以研究Na[化学式：见原文]F（[化学式：见原文] = Mn、Ni、Zn）的高压相图。预测NaZnF在约9吉帕时会发生从Pv-[化学式：见原文]到pPv-[化学式：见原文]的两次重构相变，在约26吉帕时会发生从pPv-[化学式：见原文]到ppPv-[化学式：见原文]的相变。而NaMnF的情况并非如此——在约12吉帕时从Pv-[化学式：见原文]到ppPv-[化学式：见原文]相发生直接相变（本质上是重构相变，但具有相同的Pnma空间群）。引人注目的是，我们的模拟结果表明，在此过程中发现了NaZnF后钙钛矿的一个歧化相，这为实验中的观测结果提供了成功的解释。此外，还研究了四种NaZnF相的力学和热学性质，特别是动力学性质。在此，我们揭示了在从pPv-[化学式：见原文]到ppPv-[化学式：见原文]的转变中，[化学式：见原文]波速度和体声速明显软化，这可能导致地震波在地球内部传播的不连续性。
