Thomas Young Centre and Department of Physics, Imperial College London, London SW7 2AZ, United Kingdom.
TCM Group, Cavendish Laboratory, University of Cambridge, J. J. Thomson Avenue, Cambridge CB3 0HE, United Kingdom.
Phys Rev Lett. 2014 Apr 25;112(16):165501. doi: 10.1103/PhysRevLett.112.165501. Epub 2014 Apr 22.
A theoretical study is reported of the molecular-to-atomic transition in solid hydrogen at high pressure. We use the diffusion quantum Monte Carlo method to calculate the static lattice energies of the competing phases and a density-functional-theory-based vibrational self-consistent field method to calculate anharmonic vibrational properties. We find a small but significant contribution to the vibrational energy from anharmonicity. A transition from the molecular Cmca-12 direct to the atomic I41/amd phase is found at 374 GPa. The vibrational contribution lowers the transition pressure by 91 GPa. The dissociation pressure is not very sensitive to the isotopic composition. Our results suggest that quantum melting occurs at finite temperature.
本文报道了高压下固体氢的分子-原子转变的理论研究。我们使用扩散量子蒙特卡罗方法计算了竞争相的静态晶格能，并使用基于密度泛函理论的振动自洽场方法计算了非谐振动性质。我们发现非谐振动对振动能有很小但显著的贡献。在 374 GPa 时，发现从分子 Cmca-12 直接到原子 I41/amd 相的转变。振动贡献将转变压力降低了 91 GPa。离解压力对同位素组成不是很敏感。我们的结果表明，量子熔化在有限温度下发生。
