Abstract

Density-functional theory (DFT) is applied to the calculation of the equation of state, the pair correlation function (PCF), and the static electrical conductivity of solid hydrogen near the transition point to the conducting state. It is found that the pressure versus density exhibits hysteresis at temperature of 100 K under compression followed by expansion. The overlapping of the isotherm branches of molecular and nonmolecular phases of solid hydrogen is observed, which corresponds to the domain of existence of metastable states. The value of this region is 275 GPa. Under compression, a transition of solid molecular hydrogen from monoclinic structure with C2/c symmetry to a conducting nonmolecular state with orthorhombic C222₁ structure through an intermediate conducting molecular phase with orthorhombic Cmca-4 structure is observed. Under expansion, a transition of the conducting nonmolecular state with C222₁ symmetry of the unit cell to a conducting molecular phase with Cmca-4 symmetry occurs through an intermediate nonmolecular phase with P2₁/c symmetry. It is shown that the conducting nonmolecular crystalline hydrogen with P2₁/c symmetry persists down to a pressure of 350 GPa.

中文翻译：

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亚稳态导电固体氢形成从头算动力学的模拟

摘要

密度泛函理论（DFT）用于计算状态方程，对相关函数（PCF）和在过渡到导电态的转变点附近的固体氢的静态电导率。发现压力对密度在压缩之后在100K的温度下表现出滞后，然后膨胀。观察到固体氢的分子和非分子相的等温线分支的重叠，这对应于亚稳态存在域。该区域的值为275 GPa。在压缩下，固体分子氢从具有C 2 / c对称性的单斜结构转变为具有正交C 222 ₁的导电非分子态观察到通过具有正交Cmca -4结构的中间导电分子相形成的结构。在膨胀下，通过具有P 2 ₁ / c对称性的中间非分子相，发生了晶胞具有C 222 ₁对称性的导电非分子态向具有Cmca -4对称性的导电分子相的转变。结果表明，具有P 2 ₁ / c对称性的导电非分子结晶氢一直持续到350 GPa的压力。