Hydrogen metallization under stable conditions is a substantial step towards the realization of the first room-temperature superconductor. Recent low-temperature experiments^1,2,3 report different metallization pressures, ranging from 360 GPa to 490 GPa. In this work, we simulate the structural properties and vibrational Raman, infrared and optical spectra of hydrogen phase III, accounting for proton quantum effects. We demonstrate that nuclear quantum fluctuations downshift the vibron frequencies by 25%, introduce a broad lineshape into the Raman spectra and reduce the optical gap by 3 eV. We show that hydrogen metallization occurs at 380 GPa in phase III due to band overlap, in good agreement with transport data². Our simulations predict that this state is a black metal—transparent in the infrared—so the shiny metal observed at 490 GPa (ref. ¹) is not phase III. We predict that the conductivity onset and optical gap will substantially increase if hydrogen is replaced by deuterium, underlining that metallization is driven by quantum fluctuations and is thus isotope-dependent. We show how hydrogen acquires conductivity and brightness at different pressures, explaining the apparent contradictions in existing experimental scenarios^1,2,3.

在稳定条件下进行氢金属化是实现第一个室温超导体的重要一步。最近的低温实验^1,2,3报告了不同的金属化压力，范围从360 GPa到490 GPa。在这项工作中，我们模拟了氢相III的结构特性，振动拉曼光谱，红外光谱和光谱，这说明了质子量子效应。我们证明，核量子涨落将荧光子频率下移25％，将宽线形引入拉曼光谱，并将光学间隙减小3 eV。我们表明，由于能带重叠，第三阶段在380 GPa处发生了氢金属化，与传输数据²吻合得很好。我们的模拟预测该状态是黑色金属（在红外中是透明的），因此在490 GPa（参考¹）下观察到的发亮金属不是III相。我们预测，如果氢被氘取代，则电导率的起始和光学间隙将显着增加，这表明金属化是由量子涨落驱动的，因此与同位素有关。我们展示了氢如何在不同压力下获得电导率和亮度，解释了现有实验场景^1,2,3中的明显矛盾。