氢在Mg_2Ni(100)面的吸附及扩散

Adsorption and Diffusion of H on Mg_2Ni(100) Surface

运用第一性原理研究氢在清洁和掺杂Al的Mg2Ni(100)面的吸附及扩散.在清洁Mg2Ni(100)表面,氢原子可稳定地吸附于Mg-Ni桥位和Mg-Mg桥位,吸附能为1.19-1.52eV.在掺杂Al的Mg2Ni(100)表面,氢原子可稳定吸附于Al-Ni、Mg-Ni、Mg-Al桥位,吸附能为0.10-0.29eV.氢在掺杂Al的Mg2Ni(100)表面的吸附能低于其在清洁表面的吸附能,说明掺杂Al后氢原子与表面的相互作用减弱.过渡态计算结果表明,氢原子由清洁的Mg2Ni(100)面及掺杂Al的Mg2Ni(100)面扩散至次表层的势垒分别为0.59及-0.04eV,掺杂Al后氢原子的扩散势垒降低,说明氢原子更易由掺杂Al表面扩散至次表层.Al原子替代Mg2Ni(100)面的Mg原子减弱氢原子与表面的相互作用,降低氢原子由表层扩散至次表层的势垒,这可能是Mg2Ni合金掺杂Al可改善其吸氢动力学性能的主要原因之一.

First-principles were used to investigate hydrogen adsorption and diffusion on clean and Al doped Mg2Ni（100） surfaces.The calculation results show that H prefers to adsorb onto Mg-Ni bridge sites and Mg-Mg bridge sites on a clean Mg2Ni（100） surface,and their adsorption energies range from 1.19 to 1.52 eV.For the Al doped Mg2Ni（100） surface,H prefers to adsorb onto the Al-Ni,Mg-Ni,Mg-Al bridge sites and the adsorption energies range from 0.10 to 0.29 eV.The results indicate that the Al doped Mg2Ni（100） surface reduces the adsorption energy for hydrogen.The transition state calculation shows that the energy barrier for H that diffuses from the clean and the Al doped Mg2Ni（100） surface to the subsurface is 0.59 and-0.04 eV,respectively.Doping the Mg2Ni（100） surface with Al weakens the interaction between H and the surface,and also reduces the barrier for hydrogen diffusion,which may be one reason for improving the kinetic properties of hydrogen adsorption for Mg2Ni alloy doped with Al.