The molecular Monte Carlo method, combined with the interatomic potential from Cooper, is used for the first time to investigate stoichiometric mixed oxides U_1-yPu_yO₂ (with y in the range 0–1). The implementation of this Monte Carlo method for mixed oxides simulation was carried out involving two algorithms, one without cation exchanges and another with cation exchanges. The use of these two Monte Carlo algorithms allowed us to test the effect of the substitutional disorder implied by the coexistence of two types of cations. Structural, thermodynamic and mechanical properties of stoichiometric mixed oxides fuel U_1-yPu_yO₂ have been investigated over a wide temperature range (from 300 K to the melting temperature) and plutonium content (from 0 to 100 at %). Our study shows that the exploration of cationic configurations through the cation exchange algorithm is required for a complete description of mixed oxides fuel properties especially atomic structural properties. Concerning thermodynamic properties, the curves presenting the evolution of the computed specific heat in regard with temperature show one peak for all plutonium contents around 2300 K i.e. at ∼0.8 T_m with T_m the melting temperature. The same behaviour is observed for the linear thermal expansion coefficient. These peaks, also observed in previous studies, are related to the Bredig transition known to occur around 0.8 T_m. A good agreement between our results, experiments and previous calculations is found up to about 2100 K. Above this temperature our calculations show a behaviour different from experimental recommendations.

首次将分子蒙特卡罗方法与库珀的原子间电势相结合，用于研究化学计量的混合氧化物U _1-y Pu _y O ₂（y在0-1范围内）。蒙特卡罗方法用于混合氧化物模拟的实现涉及两种算法，一种不使用阳离子交换，另一种使用阳离子交换。这两种蒙特卡洛算法的使用使我们能够测试两种类型阳离子共存所暗示的取代障碍的影响。化学计量混合氧化物燃料U _1-y Pu _y O _2的结构，热力学和机械性能已在较宽的温度范围（从300 K到熔化温度）和p含量（从0到100 at％）下进行了研究。我们的研究表明，通过阳离子交换算法探索阳离子构型是完整描述混合氧化物燃料特性（尤其是原子结构特性）的必要条件。关于热力学性质，表示所计算的比热随温度变化的曲线在2300 K附近显示了所有p含量的一个峰值，即在约0.8 T _m和T _m处。熔化温度。对于线性热膨胀系数，观察到相同的行为。这些峰，在以前的研究中也观察到，与已知在0.8 T _m左右发生的布雷迪格跃迁有关。在大约2100 K的温度下，我们的结果，实验和先前的计算之间找到了很好的一致性。在此温度以上，我们的计算显示出与实验建议不同的行为。