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arXiv 1708.01075cond-mat.mtrl-sciphysics.chem-phphysics.comp-ph
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高压固体氢中范德华力和交换作用的作用

The role of van der Waals and exchange interactions in high-pressure solid hydrogen

Sam Azadi, Graeme J. Ackland

摘要:

本文研究了固体分子氢结构中的范德华相互作用。我们计算焓和吉布斯自由能,分别获得零温度和有限温度相图。我们采用密度泛函理论(DFT)计算电子结构,采用密度泛函微扰理论(DFPT)和vanderWaals(vdW)泛函计算声子谱。我们专注于固体分子$C2/c$,$Cmca$-12,$P6_3/m$,$Cmca$,和$Pbcn$结构的压力范围内的200 $<$ P $<$ 450 GPa。我们提出了两种结构的$C2/c$和$Pbcn$的第三阶段,这是稳定在不同的压力范围内超过200 GPa。我们发现vdW泛函对振动和有限温度相稳定性有很大的影响,但是不同的vdW泛函有不同的影响。我们的结论是,除了VDW相互作用,正确的治疗高电荷梯度限制是必不可少的。我们表明,交换相关的分子键长的依赖性也有相当大的影响,计算的金属化压力,引入误差高达100 GPa。

英文摘要:

We investigate the van der Waals interactions in solid molecular hydrogen structures. We calculate enthalpy and the Gibbs free energy to obtain zero and finite temperature phase diagrams, respectively. We employ density functional theory (DFT) to calculate the electronic structure and Density functional perturbation theory (DFPT) with van der Waals (vdW) functionals to obtain phonon spectra. We focus on the solid molecular $C2/c$, $Cmca$-12, $P6_3/m$, $Cmca$, and $Pbcn$ structures within the pressure range of 200 $<$ P $<$ 450 GPa. We propose two structures of the $C2/c$ and $Pbcn$ for phase III which are stabilized within different pressure range above 200 GPa. We find that vdW functionals have a big effect on vibrations and finite-temperature phase stability, however, different vdW functionals have different effects. We conclude that, in addition to the vdW interaction, a correct treatment of the high charge gradient limit is essential. We show that the dependence of molecular bond-lengths on exchange-correlation also has a considerable influence on the calculated metallization pressure, introducing errors of up to 100GPa.

机构、总结、中文摘要均由AI分析而来,可能存在错误,请以论文正文为准。

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