MgH₂ is one of the most promising materials for solid-state hydrogen storage, but its slow kinetics and relatively high dehydrogenation temperature have yet to be overcome. We have theoretically investigated surface energy and surface H vacancy formation on various MgH₂ surfaces, including all possible H vacancy configurations in the studied size of MgH₂(110), (100), (101), and (001), up to (3 × 2), (2 × 3), (2 × 2) and (2 × 2) slabs respectively, based on density functional theory. Consequently, the hydrogen diffusion paths on the surfaces are also studied. The most unstable surface, MgH₂(001), has the most drastic change in vacancy formation energy. The relative high barriers for vacancy H formation, especially on the most stable surface, MgH₂(110), reflect the slow kinetics of H release. The introduction of vacancy into MgH₂ surfaces often induces defect levels in the energy-gap region. In general, the release of surface H atoms exhibits a pronounced dependence on the surface stability and the concentration of surface H vacancy, in line with the remarkable effect of ball milling in experiments.

MgH ₂是用于固态氢存储的最有前途的材料之一，但其缓慢的动力学和相对较高的脱氢温度仍有待克服。我们已经从理论上研究的表面能和表面H，空位形成各种的MgH _2层的表面，包括所有可能的在的MgH的所研究的口径H空位配置₂（110），（100），（101）和（001），直到（基于密度泛函理论，分别为3×2），（2×3），（2×2）和（2×2）平板。因此，还研究了表面上的氢扩散路径。最不稳定的表面，MgH ₂（001），空缺形成能量变化最大。空位H形成的相对较高的壁垒，特别是在最稳定的表面MgH ₂（110）上，反映了H释放的缓慢动力学。将空位引入MgH ₂表面通常会在能隙区域中引起缺陷水平。通常，表面H原子的释放表现出对表面稳定性和表面H空位浓度的显着依赖性，这与球磨在实验中的显着效果一致。