First-principles study on the structural and electronic properties of LiB and its hydrides (Li_2B_nH_n, n=5, 8, 12, LiBH_4)

摘要

Structural, electronic and vibrating properties of LiB and its hydrides (Li2B_nH_n, n=5, 8, 12, LiBH_4) were calculated by the first-principles using density functional theory in its generalized gradient approximation. The calculated results are in good agreement with experimental studies. The deviation between theory and experimental results are also discussed. With the increasing of H atoms in range of 512, the band gap energy increases and the width of the conduction band decreases. Comparing with LiB, the band gap of LiBH_4 is broadened, which indicates the enhancement of LiB and LiH bond strength. Valence electrons mainly transfer from Li atoms to B and H atoms. As a result, Li atoms are thought to be partially ionized as Li cations. There is little contribution of Li orbital to the occupied states, resulting in LiH and Li-B bond exhibiting an ionic nature, and BH bond showing a covalent nature.