Quantum phase diagram of high-pressure hydrogen

The interplay between electron correlation and nuclear quantum effects makes our understanding of elemental hydrogen a formidable challenge. Here, we present the phase diagram of hydrogen and deuterium at low temperatures and high-pressure (P > 300 GPa) by accounting for highly accurate electronic and nuclear enthalpies. We evaluated internal electronic energies by diffusion quantum Monte Carlo, while nuclear quantum motion and anharmonicity have been included by the stochastic self-consistent harmonic approximation. Our results show that the long-sought atomic metallic hydrogen, predicted to host room-temperature superconductivity, forms at 577±10 GPa (640±14 GPa in deuterium). Indeed, anharmonicity pushes the stability of this phase towards pressures much larger than previous theoretical estimates or attained experimental values. Before atomization, molecular hydrogen transforms from a metallic phase III to another metallic structure that is still molecular (phase VI) at 422±40 GPa (442±30 GPa in deuterium). We predict clear-cut signatures in optical spectroscopy and DC conductivity that can be used experimentally to distinguish between the two structural transitions. According to our findings, the experimental evidence of metallic hydrogen has so far been limited to molecular phases.
The data uploaded here contains the structural information of the simulated phases of hydrogen and their quantum centroid position as a function of pressure and isotope.

电子关联与核量子效应之间的相互作用，使得我们对单质氢的认知成为一项极具挑战性的难题。本研究通过计入高精度的电子与核焓，构建了低温高压（压强P＞300吉帕）下氢与氘的相图。我们采用扩散量子蒙特卡洛（diffusion quantum Monte Carlo）方法计算了内部电子能量，并通过随机自洽简谐近似（stochastic self-consistent harmonic approximation）纳入了核量子运动与非简谐效应。
我们的结果表明，长期以来备受关注的、被预测可实现室温超导的原子态金属氢，其形成压强为577±10吉帕（氘则为640±14吉帕）。值得注意的是，非简谐效应使得该相的稳定压强远高于此前的理论预估与实验可达值。在发生原子化之前，分子氢会从金属性相III转变为另一种仍保持分子结构的金属相（相VI），转变压强为422±40吉帕（氘则为442±30吉帕）。我们预测了光谱学与直流导电性方面的明确特征，可用于实验区分这两种结构相变。根据本研究结果，目前已有的金属氢实验证据仅局限于分子相。
本次上传的数据包含氢的模拟相的结构信息，以及其量子质心位置随压强与同位素种类的变化关系。