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Search for superconductivity in LiBC at high pressure: Diamond anvil cell experiments and first-principles calculations

机译：在高压下寻找LiBC中的超导电性：金刚石砧细胞实验和第一性原理计算

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Diamond anvil cell experiments augmented by first principles calculations have been used to investigate the behavior at high pressure of lithium borocarbide (LiBC), which is structurally and electronically similar to the superconductor MgB_2. It is found to remain stable up to 60 GPa with no crystal structure change and without a previously reported lattice parameter anomaly. Large anisotropy in the linear compressibility of the layered hexagonal structure is identified and related to the distinctly different bonding types within and between the hexagonal planes; a mixture of covalent and ionic intralayer bonding and interlayer bonding consisting of van der Waals-type interactions and weak (but increasing under pressure) covalency. Metallization is not found until a calculated pressure of at least 345 GPa, and pressure removes the similarity in electronic structure between LiBC and MgB_2; reducing the cell volume causes an increase in the σ and π electronic band gaps. Metallization is finally an indirect gap closure and the holes do not go into any sigma bands, ruling out the possibility of a new MgB_2-type high-pressure superconductor.
机译：通过第一原理计算得到的增强的金刚石砧室实验已用于研究硼碳化锂（LiBC）在高压下的行为，该结构在结构和电子方面均与超导体MgB_2相似。发现它在高达60 GPa的情况下仍保持稳定，没有晶体结构变化，也没有先前报道的晶格参数异常。层状六边形结构的线性可压缩性存在较大的各向异性，并且与六边形平面内和六边形平面之间明显不同的键合类型有关；共价和离子内层键合以及层间键合的混合物，由范德华型相互作用和弱（但在压力下会增加）的共价组成。直到计算出的压力至少为345 GPa才发现金属化，并且压力消除了LiBC和MgB_2之间的电子结构相似性；减小单元体积会导致σ和π电子带隙的增加。最后，金属化是间接的间隙闭合，并且孔不进入任何sigma带，从而排除了新型MgB_2型高压超导体的可能性。

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