氮掺杂氢化镥潜在母体结构的结构、振动及光学性质的从头算研究
Ab initio study of the structural, vibrational and optical properties of potential parent structures of nitrogen-doped lutetium hydride
AI总结：
针对氮掺杂氢化镥近常压超导报道的实验矛盾，本研究通过第一性原理计算其两种潜在母体结构LuH₂、LuH₃的性质，明确实验主成分为八面体位点带额外氢的LuH₂，且二者均无高温超导性。
AI中文摘要：
近期有研究报道氮掺杂氢化镥可在近常压条件下实现超导，这一结论引发了大量实验研究，但所得结果相互矛盾。我们采用第一性原理方法，对该报道中超导体的两种可能母体结构——LuH₂和LuH₃的物理性质进行了建模计算。研究表明，仅LuH₃的声子能带结构能解释已报道的拉曼光谱，原因是其八面体间隙位点存在氢原子；不过该结构仅在6 GPa以上的压力下，才会通过非简谐效应实现稳定。我们发现，报道中超导体随压力发生的奇特颜色变化，与LuH₂的光学性质相符，这种性质由无阻尼带间等离激元的存在决定：等离激元会随压力发生蓝移，无需任何结构相变即可改变样品的颜色。我们的研究结果表明，实验中的主要成分为LuH₂，且其八面体位点存在一些额外氢原子；LuH₂和LuH₃均无法在高温下实现超导。
英文摘要：
The recent report of near-ambient conditions superconductivity in a nitrogen-doped lutetium hydride has inspired a large number of experimental studies with contradictory results. We model from first principles the physical properties of the possible parent structures of the reported superconductor, LuH$_2$ and LuH$_3$. We show that only the phonon band structure of LuH$_3$ can explain the reported Raman spectra due to the presence of hydrogens at the interstitial octahedral sites. However, this structure is stabilized by anharmonicity only above 6 GPa. We find that the intriguing color change with pressure in the reported superconductor is consistent with the optical properties of LuH$_2$, which are determined by the presence of an undamped interband plasmon. The plasmon blue-shifts with pressure and modifies the color of the sample without requiring any structural phase transition. Our findings suggest that the main component in the experiments is LuH$_2$ with some extra hydrogen atoms at octahedral sites. None of LuH$_2$ and LuH$_3$ superconduct at high temperatures.
