arXiv 1505.047002015-05-18cond-mat.mtrl-sci

二硫化碳的高压层状结构

High pressure layered structure of carbon disulfide

S. Shahab Naghavi, Yanier Crespo, Roman Martonak, Erio Tosatti

备注：: 8 pages, 8 figures
发表信息：: Phys. Rev. B 91, 224108 (2015)
DOI：: 10.1103/PhysRevB.91.224108

摘要：

固体CS $_{2}$表面上类似于CO $_{2}$，在低压下具有相同的$Cmca$分子晶体结构，这表明在高压下也有类似的相。为了确定CS $_{2}$的零温最低焓结构，我们进行了广泛的第一性原理演化搜索，以增加压力高达200\，GPa。令人惊讶的是，分子$Cmca$相不像在CO $_{2}$中那样演变成$β$ -方石英，而是转变成最近在高压SiS $_{2}$中描述的相HP 2和HP 1。特别是HP 1，具有宽的稳定性范围，是层状$P2_{1}/c$结构，其特征在于边缘共享四面体对，并且理论上比迄今为止讨论的所有其他CS $_{2}$相更坚固。其拉曼光谱和对相关函数的预测值比$β$ -方石英的拉曼光谱和对相关函数的预测值更符合实验结果，并且预测了它们各自的红外光谱之间的进一步差异。计算了HP 1-CS $_{2}$的带隙在压力下接近50 GPa，产生绝缘体-金属转变，与实验观察一致。然而，金属态密度在此压力以上保持适度，表明所报道的超导性的不同起源。

英文摘要：

Solid CS$_{2}$ is superficially similar to CO$_{2}$, with the same $Cmca$ molecular crystal structure at low pressures, which has suggested similar phases also at high pressures. We carried out an extensive first principles evolutionary search in order to identify the zero temperature lowest enthalpy structures of CS$_{2}$ for increasing pressure up to 200\,GPa. Surprisingly, the molecular $Cmca$ phase does not evolve into $β$-cristobalite as in CO$_{2}$, but transforms instead into phases HP2 and HP1, both recently described in high pressure SiS$_{2}$. HP1 in particular, with a wide stability range, is a layered $P2_{1}/c$ structure characterized by pairs of edge-sharing tetrahedra, and theoretically more robust than all other CS$_{2}$ phases discussed so far. Its predicted Raman spectrum and pair correlation function agree with experiment better than those of $β$-cristobalite, and further differences are predicted between their respective IR spectra. The band gap of HP1-CS$_{2}$ is calculated to close under pressure yielding an insulator-metal transition near 50 GPa in agreement with experimental observations. However, the metallic density of states remains modest above this pressure, suggesting a different origin for the reported superconductivity.

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