First principles study of H2 molecule adsorption on Li3 N(110) surfaces

The adsorption of H2 on a Li3N(110) crystal surface is studied by first principles. Preferred adsorption sites, adsorption energy, dissociation energy and electronic structure of the H2/Li3N(110) systems are calculated separately. It is found that H2 is adsorbed on the N bridge site more favorably than on the other sites, while two NH radicles are formed on the Li3N(110) crystal surface. The calculated adsorption energy on the N bridge site is 1.909 eV, belonging to a strong chemical adsorption. The interaction between H2 and Li3N(110) surface is due mainly to the overlapping among H 1s, N 2s and N 2p states, through which covalent bonds are formed between N and H atoms. An activation barrier of 1.63 eV is found for the dissociation of H2 molecule in N bridge configuration, which indicates that the dissociative adsorption of H2 on Li3N(110) surface is favorable under the certain heat activation condition; NH2 radicle is formed after the optimization of H2 adsorbed on the N top site. The adsorption energy on the N top site is negative. In other words, this adsorption is unstable. So it is concluded that it is not easy to produce the LiNH2 between Li3N(110) face and H2 directly.