The roles of native defects and transition-metal additives (Ti, Sc and Ni) in the dehydrogenation of Mg(AlH₄)₂ hydride were investigated by First-principles calculations based on density functional theory. The elementary native defects including ${\text{H}}_{\mathit{i}}^{-}{\text{, V}}_{\text{H}}^{+}$, ${\text{V}}_{\text{H}}^{-}$, ${\left({\text{H}}_2\right)}_i^{\text{0}}$, ${\text{V}}_{\text{Mg}}^{2-}$, ${\text{Mg}}_i^{2+}$, and ${\text{V}}_{{\text{AlH}}_4}^{+}$ in Mg(AlH₄)₂ were identified. Based on the formation and migration of dominant defects, we proposed a dehydrogenation mechanism of Mg(AlH₄)₂. The formation of the dominant defect ${\text{V}}_{{\text{AlH}}_4}^{+}$ is the rate-limiting step in the dehydrogenation process. The highly mobile ${\text{H}}_i^{-}$ diffuses into the lattice and binds with Mg²⁺ to produce MgH₂ phase. In the transition metal doped hydrides, interstitial defects Ti_i and Sc_i cause the Fermi-level shift to the left and lead to the decrease of the formation energy and activation energy of ${\text{V}}_{{\mathrm{AlH}}_4}^{+}$, which is beneficial to the dehydrogenation of Mg(AlH₄)₂. This study presents an in-depth understanding on the roles of native defects and transition metal additives in the dehydrogenation process of Mg(AlH₄)₂ hydride.

通过基于密度泛函理论的第一性原理计算，研究了天然缺陷和过渡金属添加剂（Ti，Sc和Ni）在Mg（AlH ₄）₂氢化物脱氢中的作用。基本的自然缺陷包括${\text{H}}_{\mathit{一世}}^{-}{\text{，V}}_{\text{H}}^{+}$， ${\text{V}}_{\text{H}}^{-}$， ${（{\text{H}}_2）}_{\mathrm{一世}}^{\text{0}}$， ${\text{V}}_{\text{镁}}^{2-}$， ${\text{镁}}_{\mathrm{一世}}^{2+}$和 ${\text{V}}_{{\text{铝}}_4}^{+}$在Mg（AlH ₄）_2中被鉴定。基于主要缺陷的形成和迁移，我们提出了Mg（AlH ₄）₂的脱氢机理。主要缺陷的形成${\text{V}}_{{\text{铝}}_4}^{+}$是脱氢过程中的限速步骤。高度移动${\text{H}}_{\mathrm{一世}}^{-}$扩散到晶格中并与Mg ²⁺结合产生MgH ₂相。在过渡金属掺杂的氢化物中，间隙缺陷Ti _i和Sc _i导致费米能级向左移动，并导致形成能和活化能的降低。${\text{V}}_{{铝}_4}^{+}$，有利于Mg（AlH ₄）₂的脱氢。这项研究提出了对天然缺陷和过渡金属添加剂在Mg（AlH ₄）₂氢化物的脱氢过程中的作用的深入了解。