New modulated structures of solid bromine at high pressure
New modulated structures of solid bromine at high pressure
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高压固体溴的新调制结构
DOI：
10.1016/j.commatsci.2019.109205
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发表时间：
2020
影响因子：
3.3
通讯作者：
Weihua Wang
中科院分区：
文献类型：
--
作者：
Peifang Li;Xindi Du;Guoying Gao;Rongxin Sun;Lijuan Zhang;Weihua Wang
采用先进的结构搜索方法结合第一性原理计算，研究了加压下溴的晶体结构。在10和90 GPa，我们成功地再现了实验观察到的分子相I和单原子体心斜方相II，分别。在120和200 GPa下，预测的最低焓结构分别是体心四元和面心立方相，这也与以前的理论研究一致。有趣的是，在50-80 GPa的压力范围内，我们的结构搜索预测了四个结构相似和调制的结构，oF 20，oC 24，oF 28和oC 12，其调制矢量的大小分别为2/5，1/6，2/7和1/3。焓计算表明，oF_（20）、oC_（24）、oF_（28）和oC_（12）分别在52-53、53-58、58-65和65-79 GPa的压力范围内是热力学稳定的。通过比较溴中预测的oF 28、oC 12和碘中已知的无公度调制相V的结构表征和X射线衍射图案，我们认为溴也可能采用无公度调制结构。此外，在分子相I和非公度相之间存在两个新相（oF 20和oC 24），这与拉曼散射和X射线吸收光谱（XAS）实验结果一致.首次给出了溴的分子相I和单原子相II之间的结构信息。计算的弹性刚度系数表明，四个调制相位是机械稳定的。这四个预测相的电子态密度的计算表明，它们都是金属。
Crystal structures of bromine under pressure have been studied through the advanced structure search method in combination with first-principles calculations. At 10 and 90 GPa, we successfully reproduced the experimentally observed molecular phase I and monatomic body-centred orthorhombic phase II, respectively. At 120 and 200 GPa, the lowest-enthalpy structures predicted are body centered tetragonal and face-centered cubic phase, respectively, which are also consistent with previously theoretical study. Interestingly, in the pressure range of 50–80 GPa, our structural searches predicted four structurally similar and modulated structures, oF20, oC24, oF28 and oC12, whose magnitude of the modulation vectorskare 2/5, 1/6, 2/7 and 1/3, respectively. Enthalpy calculations show that oF20, oC24, oF28 and oC12 are thermaldynamically stable in the pressure range of 52–53, 53–58, 58–65 and 65–79 GPa, respectively. Through comparison of the structural characterization and X-ray diffraction patterns of the predicted oF28, oC12 in bromine and the known incommensurate modulated phase V in iodine, we suggest that bromine might also adopt an incommensurate modulated structure. In addition, the prediction of two new phases (oF20 and oC24) between molecular phase I and incommensurate phases are consistent with Raman scattering and X-ray absorption spectroscopy (XAS) experimental results. For the first time, we presented the structure information between molecular phase I and monatomic phase II in bromine. The calculated elastic stiffness coefficients indicate that the four modulated phases are mechanically stable. The calculated electronic density of states for these four predicted phases show that they are all metallic.
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