LiN_2H_3BH_3和LiNH_2BH_3储氢材料的第一性原理计算

First-principles Calculations of Materials for Hydrogen Storage of LiN_2H_3BH_3 and LiNH_2BH_3

运用基于密度泛函理论框架下的第一性原理方法,研究了储氢材料LiNH_2BH_3的高温相(α-LiHB),低温相(β-LiHB)和LiNH_2BH_3(LiAB)的晶体结构,能带结构,态密度以及化学键性质。氢原子解离能的计算表明与Li^+相邻的H^(δ+)(N1)在初始析氢阶段起主导作用,低温β-LiHB较高温α-LiHB更易于析氢。然后,通过Dmol3计算的HOMO和LUMO图表明α-LiHB可能析氢途径为H-N_1…B和H-N_2…B,而β-LiHB和LiAB仅有H-N_1…B途径。HOMO-LUMO的能隙大小表明LiAB,α-LiHB和β-LiHBH的化学稳定性为:LiAB>α-LiHB>β-LiHB。以上所有研究都为实验合成的多相LiHB提供了一定的理论基础。

Based on the first-principles density functional theory, the crystal structures, band structures, densities of states and chemical bond properties of high-temperature phase（short for α-LiHB）, low-temperature phase（short for β-LiHB） in LiN2H3BH3 and LiNH2BH3（short for LiAB） materials for hydrogen storage were studied. The calculated hydrogen removal energies show that Hδ＋（N1） adjacent to Li＋ plays a major role in the initial stage of dehydrogenation and low-temperature phase β-LiHB is easier to desorb hydrogen than high-temperature phase α-LiHB. Then, HOMO and LUMO calculated by Dmol3 indicate that dehydrogenation of α-LiHB is through H-N1…B and H-N2…B, while that of β-LiHB and LiAB are only through H-N1…B. The energy gap of HOMO-LUMO suggests that chemical stability order of LiAB, α-LiHB and β-LiHBH is： LiABα-LiHBβ-LiHB. All the researches provide a theoretical basis for the synthesis of polyphase LiHB in some way.