金属性硅同素异形体的第一性原理研究

First-Principles Investigations on Metallic Silicon Allotropes

从理论上提出了一种新型金属性硅的同素异形体hP12-Si。hP12-Si结构可以看作是由六元环形成的一种隧道型结构,与之前报道的Si24结构近似。弹性常数和声子谱的计算结果验证了该结构在常压下的稳定性。通过结构遗传性和热力学稳定性分析表明,可以效仿Si24的制备方法,通过预先合成出高压前驱物LiSi12再除去其中的Li原子来获得hP12-Si。在这种结构中,有一半的硅原子为5配位,其他硅原子为4配位。电子结构计算表明,该结构具有金属导电性,导电性主要是由于5配位原子的存在导致价电子具有离域性。

A new metallic metastable silicon allotrope hP12-Si has been theoretically proposed using the particle swarm optimization method. The hP12-Si structure can be seen as a combination of a tunnel-type structure formed from six-membered sp3 silicon rings, which is similar to the previously reported Si24 structure. Its stability was verified by calculating its elastic constants and phonon spectrum. The analysis of structural heritability and thermodynamic stability shows that hP12-Si might be obtained by removing Li atoms from the pre-synthetic LiSi12 precursor, which is analogous with the recent preparation of Si24. There are 50% five coordinated silicon atoms, whereas the others are four coordinated in the hP12-Si structure. Electronic band structure calculation indicated that this structure could perform the metallic properties, which might be resulted from the delocalization of valence electrons caused by the existence of five coordinated atoms.