UO2 晶体中低密勒指数晶面表面能的分子动力学模拟

采用基于刚性离子势的分子动力学模拟方法初步计算了UO₂晶体中(100), (110)和(111) 3种低密勒指数晶面在300–1500 K范围内的表面能大小. 结果表明, 3种晶面的表面能大小随温度的升高而降低, 与实验结果趋势一致; 原子排列最紧密的(111)晶面具有最低的表面能, 3种晶面的表面能大小从高到低依次为(100), (110)和(111)晶面; 达到平衡状态下的表面层原子相对于体内原子层在表面的法线方向上发生了明显的压缩并且表面层原子的对称性也降低了, 表面原子的弛豫效应一直影响到了第5层. 计算研究结果将有助于深入认识UO₂燃料中裂变气体气泡的聚集长大以及燃料的辐照肿胀开裂行为.关键词：分子动力学2')" href="#">UO₂低密勒指数晶面表面能

Molecular dynamics simulation of surface energy of low miller index surfaces in UO2

Molecular dynamics simulation based on the rigid-ion potential is carried out to investigate the surface energies of low miller index crystallographic faces such as (100), (110) and (111) in UO₂ in a temperature range of 300 K-1500 K. The results indicate that the surface energies of the three low miller index crystallographic faces decline gradually with temperature rising, and the variation of the surface energy with temperature is confirmed to be consistent with the experimental data. The (111) crystallographic face which is the closest surface has the lowest surface energy; the (100) crystallographic face has the biggest surface energy; the (100) crystallographic face has a surface energy in between them. The surface atoms have compressed towards the vertical line of surface with respect to the inside atoms layer obviously. The symmetry of surface atoms declines. Surface phenomena such as relaxation and reconstruction occur on the surface atoms and the relaxation effect extends to the five layers. The results presented in the study are useful for understanding the behaviors of fission gas bubbles growing up and cracking up due to the swelling in fuels under the irradiation.
Keywords：molecular dynamics2')" href="#">UO₂low miller index surfacesurface energy