Helium (He) trapping at carbide precipitates is significant for understanding the macroscopic effects of He in the normal reduced activation ferritic/martensitic (RAFM) steels and castable nanostructured alloys (CNAs) under irradiation. In this study, the behavior of intrinsic point defects and He impurities in VC is investigated by first-principles calculations. The formation of carbon (C) vacancy is quite easy and vacancy makes covalent interaction of neighboring C and V atoms more obvious. Besides, the diffusion of vacancy in VC is significantly slower than that in Fe matrix. It's worth noting that the interaction between carbon vacancies is repulsive which means that the formation of large voids maybe difficult in VC. Apart from vacancy, He impurities are also investigated. Interstitial He is less stable and diffuses more easily inside VC precipitate than inside TaC and Fe matrix. Besides, vacancy can trap much more He in VC than in Fe matrix. The result means that vacancy-abundant VC particle may have stronger ability to trap He than Fe matrix. Due to the repulsion of vacancies, we suggest that the formation of large He bubbles in VC is difficult. That is to say, little He bubbles have a dispersive distribution in VC. These theoretical results can help to understand the behavior of vacancy and He impurities in VC precipitate and further the bubble formation at precipitate in normal RAFM steels and CNAs.

氦（He）在碳化物沉淀处的捕获对于理解氦在辐射下正常还原活化的铁素体/马氏体（RAFM）钢和可铸造纳米结构合金（CNA）中的宏观影响非常重要。在这项研究中，通过第一性原理计算研究了VC中本征点缺陷和He杂质的行为。碳（C）空位的形成非常容易，并且空位使得相邻的C和V原子的共价相互作用更加明显。此外，VC中空位的扩散明显慢于Fe基体中的空位。值得注意的是，碳空位之间的相互作用是排斥性的，这意味着在VC中可能难以形成大的空隙。除了空位，还研究了He杂质。与TaC和Fe基质内部相比，间隙He的稳定性较差，并且在VC沉淀物中更容易扩散。此外，空位可以使VC中的He捕获远多于Fe基中的He。结果表明，空位丰富的VC颗粒可能比Fe基质具有更强的捕获He的能力。由于空位的排斥，我们建议在VC中很难形成大的He气泡。也就是说，几乎没有He气泡在VC中具有分散分布。这些理论结果可以帮助理解VC沉淀物中空位和He杂质的行为，并进一步了解普通RAFM钢和CNA中沉淀物中的气泡形成。由于空位的排斥，我们建议在VC中很难形成大的He气泡。也就是说，几乎没有He气泡在VC中具有分散分布。这些理论结果可以帮助理解VC沉淀物中空位和He杂质的行为，以及在普通RAFM钢和CNA中沉淀物中的气泡形成。由于空位的排斥，我们建议在VC中很难形成大的He气泡。也就是说，几乎没有He气泡在VC中具有分散分布。这些理论结果可以帮助理解VC沉淀物中空位和He杂质的行为，以及在普通RAFM钢和CNA中沉淀物中的气泡形成。