高熵合金辐照性能的计算机模拟进展

Nuclear power plays a vital role in the existing energy system and is an essential part of the clean energy that is urgently needed in the world today. Nuclear structural materials are one of the most critical factors to ensure the reliability and safety of nuclear power systems. In the future fourth-generation fission and fusion reactors, the core structural materials will be in harsh environments such as high temperature, strong chemical corrosion, and intense neutron irradiation. This extremely harsh application environment puts stringent requirements on the structural materials used for future reactors. High-energy neutrons generated by nuclear fission or nuclear fusion would cause significant atomic displacement in the material and produce point defects or defect clusters, which will degrade the performance of the material. Therefore, it is crucial to study the damage mechanism of materials under irradiation conditions and to develop new irradiation-resistant structural materials for the implementation of advanced reactors. In recent years, as a new type of alloys, high-entropy alloy (HEAs) has shown good irradiation resistance and corrosion resistance, hence they have become one of the prominent candidates for the structural materials used in the future reactors. Among various efforts to study the irradiation damage mechanism of HEAs, computational simulation has become an extraordinary method to understand their radiation resistance, since experiments would be limited by the cost and availability of the equipment.
At present, there still exist many problems in the simulation of the irradiation performance of HEAs. One of the most important factors is that the disordered state caused by the random arrangement of elements poses a significant challenge to computational methods. For example, due to the random arrangement of elements, it is difficult to define the chemical potential of each constituent element, which leads to different results in the calculation of defect energies in HEAs. Due to the large number of constituent elements, the empirical potentials for HEAs are difficult to obtain, which makes it challenging to carry out molecular dynamics simulation and other simulation methods. Moreover, the first-principles calculation method, which does not rely on the empirical potentials, is limited by computational power. It can only simulate small atomic systems, but not the nature of defect clusters and the long-term diffusion of defects. These factors are the limitations in the simulation of the irradiation performance of HEAs.
Despite these limitations, in recent years, researchers have made significant progress in the simulation of the irradiation performance of HEAs. For example, the analysis of chemical disorder helps to explain the relationship between irradiation performance and the structure of HEAs. The mechanism of defect generation under irradiation conditions is well demonstrated by analyzing the initial displacement damage and the properties of the displacement threshold energy. The sluggish diffusion effect and the preferential diffusion of defects are explored by calculating the formation and migration energy of defects. Finally, the recombination of Frenkel defects and interactions among different types of defects were also studied, which elucidate the mechanism of defect evolution in HEAs.
In this paper, we review recent progress on computer simulation of irradiation performance of HEAs in recent years. First, we briefly introduce the basic properties of HEAs and several methods used for irradiation damage simulations. Then, we have discussed the irradiation damage mechanism of HEAs in five aspects as follows: 1) defect generation mechanism, 2) the energetic properties of defects, 3) defect diffusion properties, 4) defect recombination properties, and 5) the interactions among different defects. Finally, we provide some views on the current challenges and possible future directions.