Structural Prediction And Analysis Of Superconductivity In Lithium Boride

The superconductivity of metal boride has been been focused for several years sinceMgB2was founded to have a surprising Tc. So far, many studies have been concentratedon the alkaline-earth metal boride, whereas the studies reported on alkali metal boride arerare. The purpose of the study is to determine the stable phase in lithium boride and topredict the superconductivity of these structures.Based on the particle-swarm optimization method and the first principle，thestructures of LiB, Li₄B3_,Li₃B₂,Li₂B,Li₃B were predicted respectively and the stable andmetastable phase were determined. For Li4B3, Three chain structures was predicted,namely3-186（P63/MMC）,18-8（IMMA）,6-58（PNNM）. These structures are stable inenergy and mechanism, but electronic structure suggests that they are notsuperconductive. For Li₃B₂, five structures were predicted, namely2-17（P63/MCM）,3-7（CMCA）,17-191（P6/MMM）. In these structures,2-17,3-7are chain structure and theyare not superconductive.The layered structure17-191is also not superconductive. ForLi2B, the four predicted structures respectively are2-63（CMCM）,24-2（C2/M）,22-2（P-3M1）,18-12（C2/M）. In these structures,2-63and24-2belong to the chain structure,whereas the structure of22-2and18-12are layered structures, Electronic calculationsuggests that the structure2-63and24-2are not superconductive,however, both22-2and18-12are superconductive. For Li3B, two chain structures were founded and respectivelyare1-11（CMCM）,2-153（P3212）.The electronic structure indicated that two structures areconductive but not superconductive.