Structure of phase III of solid hydrogen
Structure of phase III of solid hydrogen
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DOI：
10.1038/nphys625
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发表时间：
2007-07-01
期刊：
影响因子：
19.6
通讯作者：
Needs, Richard J.
中科院分区：
文献类型：
--
作者：
Pickard, Chris J.;Needs, Richard J.
氢是元素周期表中的第一个元素，具有任何原子中最简单的电子结构，并且氢分子包含最简单的共价化学键。然而，氢的相图却知之甚少。确定固态氢的稳定结构是一个巨大的实验挑战（1-3），因为氢原子对X射线的散射很弱，导致衍射图案分辨率很低。由于结构之间的能量差很小以及质子零点运动的重要性，理论研究遇到了重大困难。我们利用第一性原理密度泛函理论（DFT）电子结构方法（4）系统地研究了固体氢的零温相图，包括质子在谐波水平上的零点运动。我们的研究导致了一个根本性的修订的DFT相图的氢高达近400 GPa。最稳定的相保持绝缘到非常高的压力消除了理论（5）和实验（6）之间的主要差异。我们的一个新阶段的计算是稳定的，在很宽的压力范围内，其振动特性与现有的实验数据相III。
Hydrogen, being the first element in the periodic table, has the simplest electronic structure of any atom, and the hydrogen molecule contains the simplest covalent chemical bond. Nevertheless, the phase diagram of hydrogen is poorly understood. Determining the stable structures of solid hydrogen is a tremendous experimental challenge(1-3), because hydrogen atoms scatter X-rays only weakly, leading to low-resolution diffraction patterns. Theoretical studies encounter major diffculties owing to the small energy differences between structures and the importance of the zero-point motion of the protons. We have systematically investigated the zero-temperature phase diagram of solid hydrogen using first-principles density functional theory (DFT) electronic-structure methods(4), including the proton zero-point motion at the harmonic level. Our study leads to a radical revision of the DFT phase diagram of hydrogen up to nearly 400 GPa. That the most stable phases remain insulating to very high pressures eliminates a major discrepancy between theory(5) and experiment(6). One of our new phases is calculated to be stable over a wide range of pressures, and its vibrational properties agree with the available experimental data for phase III.