Photodisintegration is a main energy loss process for ultrahigh-energy cosmic-ray (UHECR) nuclei in intergalactic space. Therefore, it is crucial to understand systematic uncertainty in photodisintegration when simulating the propagation of UHECR nuclei. In this work, we calculated the cross sections using the random phase approximation (RPA) of density functional theory (DFT), a microscopic nuclear model. We calculated the $E1$ strength of 29 nuclei using three different density functionals. We obtained the cross sections of photonuclear reactions, including photodisintegration, with the $E1$ strength. Then, we implemented the cross sections in the cosmic-ray propagation code CRPropa. We found that assuming certain astrophysical parameter values, the difference between UHECR energy spectrum predictions using the RPA calculation and the default photodisintegration model in CRPropa can be more than the statistical uncertainty of the spectrum. We also found that the differences between the RPA calculations and CRPropa default in certain astrophysical parameters obtained by a combined fit of UHECR energy spectrum and composition data assuming a phenomenological model of UHECR sources can be more than the uncertainty of the data.

光衰变是星际空间中超高能宇宙射线 (UHECR) 核的主要能量损失过程。因此，在模拟 UHECR 核的传播时，了解光崩解的系统不确定性至关重要。在这项工作中，我们使用微观核模型密度泛函理论 (DFT) 的随机相位近似 (RPA) 计算了横截面。我们计算了$乙\mathrm{1个}$使用三种不同的密度泛函计算 29 个原子核的强度。我们获得了光核反应的横截面，包括光致分解，$乙\mathrm{1个}$力量。然后，我们在宇宙射线传播代码 CRPropa 中实现了横截面。我们发现，假设某些天体物理参数值，使用 RPA 计算的 UHECR 能谱预测与 CRPropa 中的默认光崩解模型之间的差异可能超过光谱的统计不确定性。我们还发现，假设 UHECR 源的现象学模型，通过 UHECR 能谱和成分数据的组合拟合获得的某些天体物理参数的 RPA 计算和 CRPropa 默认值之间的差异可能大于数据的不确定性。