**2. Simulation Method**

## *2.1. Interatomic Potential*

The interatomic interaction potentials of UO2 have been widely reported previously. Among them, the potentials reported by Basak et al. [37], Morelon et al. [38], and Cooper et al. [39] are more commonly used. For the further addition of fission gas, Xe, based on UO2, and UO2–Xe interatomic interaction potentials have been mainly developed by Geng et al. [40], Chartier et al. [41], Thompson et al. [42], and Cooper et al. [43]. For the UO2–Kr system, only one interatomic interaction potential developed by Cooper et al. [43] can be presently used. These UO2–Xe and UO2–Kr potentials use the Xe and Kr potentials proposed by Tang and Toennies [44].

Herein, the UO2 potential reported by Cooper et al. [39] is adopted to describe the U–U, U–O, and O–O interactions. This potential reproduces a range of thermophysical properties, such as the lattice parameter, bulk modulus, enthalpy, and specific heat at temperatures between 300 and 3000 K, as well as some defect properties in UO2. In addition, this potential's bulk modulus and elastic constant are more accurate and in accordance with experimental values [45]. The Xe–Xe interaction is described by the Tang– Toennies potential [44]. Further, the interactions of Xe–U and Xe–O have been described by Thompson et al. [42], and are very flexible and can be applied to a wide variety of potential forms and materials systems, including metals and EAM potentials. For the UO2–Kr system, the interatomic interaction potential developed by Cooper et al. [43] is adopted.
