H_2分子在Li_3N(100)表面吸附的第一性原理研究

First Principles Study of H_2 Molecule Adsorption on Li_3N(100) Surfaces

采用第一性原理方法研究了H2分子在两种Li3N(100)晶面的表面吸附情况.通过研究Li3N(100)/H2体系的吸附位置、吸附能和电子结构,发现H2分子在Li3N(100)晶面主要是化学吸附,但也可以发生物理吸附.在表面终止原子为Li和N的Li3N(100)表面,吸附的最稳定结构中H2分子被解离,最终H原子分别趋于两个N原子的顶位,形成两个NH基,吸附能为5.157 eV,属于强化学吸附;此时H2分子与Li3N(100)表面的相互作用主要源于H1s轨道与Li3N表层N原子的2s,2p轨道重叠杂化的贡献,且N—H键为共价键.在表面终止原子为Li的Li3N(100)表面,吸附的最稳定结构中H2分子也被解离,H原子趋于穴位,吸附能为2.464 eV,也属于强化学吸附;此时Li和H之间为较强的离子键相互作用.

The adsorption of H2 on two kinds of Li3N（100） crystal surfaces has been studied by the first principles.It is found that chemical adsorption mainly happens when H2 molecules are on the Li3N（100） crystal surfaces,but physical adsorption may also happen,which is based on the studying of the adsorption sites,adsorption energy and electronic structure of the Li3N（100）/H2 systems.In the most stable structures of the absorption of the Li3N（100） surfaces on which the atoms are Li and N,the H2 molecules are dissociated.At last the H atoms tend to the two N top respectively,forming two NH.The adsorption energy is 5.157 eV.This process belongs to the strong chemical adsorption;while the interaction between H2 molecule and Li3N（100） surface is mainly due to the overlap-hybridization among H1s,N2s and N2p states,through which covalent bonds are formed between N and H atoms.In the most stable structures of the absorption of the Li3N（100） surfaces on which the atoms are Li,and the H2 molecules are also dissociated.The H atom tend to the hollow,and the adsorption energy is 2.464 eV.This process also belongs to the strong chemical adsorp-tion,while the interaction between Li and H is ionic.