Novel high pressure structures and superconductivity of niobium disulfide
Novel high pressure structures and superconductivity of niobium disulfide
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二硫化铌的新型高压结构和超导性
DOI：
10.1016/j.jallcom.2014.05.013
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发表时间：
2014-01
期刊：
影响因子：
--
通讯作者：
Zhang Xiu-Lu
中科院分区：
文献类型：
--
作者：
Liu Zhong-Li;Cai Ling-Cang;Zhang Xiu-Lu
利用密度泛函理论研究了二硫化铌（NbS2）的压致相变和超导性质。采用多算法协同（MAC）结构预测技术对0~2 0 0GPa压力下NbS2的结构进行了预测.成功地再现了以前已知的1T-、2H-和3R-NbS 2。此外，还发现了许多具有合成潜力的亚稳结构。通过焓计算发现，在26GPa下，NbS2从双六方（2H）结构转变为四氢四茂/mmm结构，体积减少了10.6%.计算的弹性常数和声子色散曲线证实了I4/mmm-NbS2在高压下的力学和动力学稳定性。更有趣的是，在I4/mmm结构中Nb的配位数为8，比传统的金属二硫属化合物中的配位数大，表明Nb和S原子之间存在一种新型的键合。在新的Nb-S键中，一个Nb原子与相邻的八个S原子形成一个[NbS8]六面体单元。此外，I4/mmm-NbS2比2H-NbS2具有更高的超导临界温度，这是由于I4/mmm-NbS2具有更强的电子-声子耦合系数。
We have investigated the pressure-induced phase transition and superconducting properties of niobium disulfide (NbS 2) based on the density functional theory. The structures of NbS 2 at pressures from 0 to 200 GPa were predicted using the multi-algorithm collaborative (MAC) structure prediction technique. The previously known 1T-, 2H-, and 3R-NbS 2 were successfully reproduced. In addition, many metastable structures which are potential to be synthesized were also discovered. Based on the enthalpy calculations, we found that at 26 GPa NbS 2 transits from the double-hexagonal (2H) structure to the tetragonal I 4/mmm structure with a 10.6% volume reduction. The calculated elastic constants and phonon dispersion curves of I 4/mmm-NbS 2 confirm its mechanical and dynamical stability at high pressure. More interestingly, the coordination number of Nb in I 4/mmm structure is eight which is larger than that in the traditional metal dichalcogenides, indicating a new type of bondings of Nb and S atoms. In the new Nb–S bondings, one Nb atom and neighboring eight S atoms form a [NbS 8] hexahedron unit. Furthermore, I 4/mmm-NbS 2 exhibits a higher superconducting critical temperature than 2H-NbS 2, as is resulted from the stronger electron–phonon coupling coefficients.
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