First principles calculations have been performed to investigate the synergetic effect of H and He impurities with vacancies in Ti₃AlC₂. The configurations and energetics of H_n–He–V_Al complexes (n ≤ 4) and He–He/He–H/H–H interactions have been studied. It is found that the impurity H atom prefers to occupy the tetrahedral interstitial site (I_tetr-3), but the He atom prefers to occupy the octahedral interstitial site (I_oct-4) in perfect Ti₃AlC₂. Within a pre-existing Al vacancy, the most favorable site for a He atom is close to tetr-site, meanwhile the H atom preferentially deviates from the vacancy center with the separation 1.3 Å along the 〈001〉 direction. He–H and He–He show a weakly attractive interaction, but weak repulsion occurs in the H–H interaction, which is different from the case of Ti₃SiC₂. The He–V_Al complex plays an important role in the trapping of H atoms. The He–V_Al cluster can trap up to three H atoms in the absence of H₂ molecules, which leads to the formation of a H–He hybridized bubble. Thus, the He atom can subsequently suppress further aggregation of H atoms and block hydrogen embrittlement and volume swelling.

中文翻译：

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H 3和He杂质在Ti ₃ AlC _2中的协同作用：第一性原理计算

已经进行了第一原理计算，以研究H和He杂质与Ti ₃ AlC _2中的空位的协同作用。的配置和H的能量学_ñ -他-V_的Al配合物（Ñ ≤4）和He-他/他-H / H-H的相互作用进行了研究。发现杂质H原子更倾向于占据四面体间隙位（I _tetr -3），而He原子更倾向于占据完美Ti ₃ AlC _2中的八面体间隙位（I _oct -4）。。在预先存在的Al空位中，He原子最有利的位置靠近四原子位，同时H原子优先偏离空位中心，沿<001>方向的间距为1.3Å。He–H和He–He表现出弱的吸引力相互作用，但在H–H相互作用中产生弱排斥力，这与Ti ₃ SiC ₂的情况不同。He-V _Al络合物在俘获H原子中起重要作用。在没有H ₂分子的情况下，He–V _Al团簇最多可以俘获3个H原子，这导致形成H–He杂化气泡。因此，He原子可随后抑制H原子的进一步聚集，并阻止氢脆和体积膨胀。