锆合金是压水堆燃料包壳的核心关键材料，其初级辐照损伤行为直接关系到反应堆的服役安全性；然而，目前锆合金中Nb元素对这一损伤行为的原子尺度调控机制仍有待明确。本工作采用分子动力学模拟方法，系统研究了Zr-xNb (x = 0.0、0.5、1.0、2.5，原子分数，%)单晶合金在不同初级碰撞原子(PKA)入射方向及在不同体系温度条件下的初级辐照损伤特征。结果表明，PKA入射方向对Frenkel缺陷对数量以及离位原子数量的影响小于1%；随体系温度升高，空位/间隙团簇尺寸呈先增大后减小的非单调变化；间隙原子Nb (I_Nb)比例远高于合金初始Nb含量，且合金初始Nb含量的增加可显著削弱间隙原子扩散的各向异性。当Nb含量为0.5%时，合金中间隙团簇尺寸增长最为明显，当Nb含量增至1.0%时，Nb的钉扎效应增强使团簇尺寸略有下降；同时随Nb含量增加，空位团簇构型由三维金字塔结构逐渐演变为二维基面型，间隙原子扩散各向异性显著减弱，有效抑制了棱柱面上间隙<a>型纳米团簇的生长，最终提升Zr-Nb合金的抗辐照生长能力。

Zr alloys represent the key material employed in the fabrication of fuel cladding for pressurized water reactors. The primary irradiation damage behavior displayed by the alloys exerts a direct influence on the operational safety of the reactors. However, the atomic-scale regulatory mechanism of Nb in this behavior remains to be elucidated. Therefore, this study employs molecular dynamics method to examine the primary irradiation damage characteristics of Zr-xNb (x = 0.0, 0.5, 1.0, 2.5; atomic fraction, %) single-crystal alloys with various primary knock-on atom (PKA) incident crystallographic directions and system temperatures. The findings suggest that the impact of the PKA incident direction on the total number of Frenkel pairs and displaced atoms is less than 1%. However, the PKA incident direction has been shown to considerably alter the proportional distribution of Nb vacancies. As the system temperature increases, the size of vacancy and interstitial clusters displays a non-monotonic variation, initially increasing and then decreasing. At 573 K, which is the typical service temperature of nuclear reactor cladding materials, there is a heightened propensity for coalescence, as evidenced by a high tendency for such processes to occur. The proportion of interstitial Nb atoms is notably higher than the nominal Nb content of the alloy. Additionally, increasing the Nb content markedly weakens the anisotropy of interstitial atom diffusion. With respect to Nb concentration, the size of interstitial clusters is maximized at 0.5%Nb; however, at 1.0%Nb, the augmented pinning effect of Nb results in a slight reduction in cluster size. The three-dimensional pyramidal structures characteristic of these systems simultaneously undergoes a transition to a two-dimensional basal-plane structure, accompanied by a notable weakening of the anisotropy of interstitial diffusion. This effect suppresses the growth of interstitial <a>-type nanoclusters on the prismatic planes and ultimately enhances the irradiation growth resistance of Zr-Nb alloys. This study clarifies the underlying mechanisms of primary irradiation damage in Zr-Nb alloys, thereby providing a theoretical foundation at the atomic scale for enhancing the irradiation resistance of these materials.