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基于密度泛函理论系统地研究了铀锆合金(γ-UZr和δ-UZr2)的晶体结构、电子结构及化学键性质。鉴于U-5f电子的强关联性,使用局域密度近似(LDA)和LDA+U(U=4eV)方法对比研究了铀锆合金的基态性质。尽管这两种方法计算所得的晶格常数均略小于实验值,但总体上与实验还是符合的很好。与纯LDA相比,加U=4eV的计算结果显示5f电子的库仑排斥作用对合金体系电子态密度分布的影响极小。因此可忽略U-5f的库仑排斥作用。两种构型合金体系的总态密度分布表明它们在费米能级附近的电子占据主要是U-5f和Zr-4d,并有明显的杂化。在γ-UZr和δ-UZr2中,U—Zr键间均显示微弱的共价性,其中U—Zr2共价性最强(0.048e/au3),U—Zr次之(0.040e/au3),U—Zr1最弱(0.032e/au3),而δ-UZr2中的Zr1离子性最强。
The crystal structure, electronic structure and chemical bond properties of uranium-zirconium alloys (γ-UZr and δ-UZr2) were systematically studied based on density functional theory. Due to the strong correlation of U-5f electrons, the ground state properties of uranium-zirconium alloys were compared using the methods of local density approximation (LDA) and LDA + U (U = 4eV). Although the lattice constants calculated by the two methods are slightly less than the experimental values, but overall in good agreement with the experiment. Compared with the pure LDA, the calculated result of adding U = 4eV shows that the Coulomb repulsion of 5f electrons has little effect on the electron density distribution of the alloy system. Therefore Coulomb repulsion of U-5f can be neglected. The total state-density distribution of the two alloy systems shows that they occupy mainly U-5f and Zr-4d near the Fermi level with obvious hybridization. In the γ-UZr and δ-UZr2, the U-Zr bonds showed weak covalency among them, among which U-Zr2 had the highest covalence (0.048e / au3), the second U-Zr (0.040e / au3) , U-Zr1 the weakest (0.032e / au3), and δ-UZr2 Zr1 ion strongest.