(Th, Pa)O2和(U, Pa)O2的结构与性质的密度泛函研究

Structure and properties of (Th, Pa)O2 and (U, Pa)O2 compound from density functional studies

摘要:

本文基于密度泛函理论的第一性原理，采用广义梯度近似的PBEsol+U方法计算了ThO2﹑PaO2﹑UO2﹑(Th, Pa)O2和(U, Pa)O2的结构、力学、电子和光学性质. 结构优化的结果表明PBEsol+U方法能对锕系氧化物ThO2﹑PaO2和UO2提供较好的晶格参数和力学参量. 计算ThO2﹑PaO2和UO2的晶格参数和带隙与实验值和相关理论值做了比较，且与实验值吻合较好. 同时，(Th, Pa)O2和(U, Pa)O2的晶格参数处于ThO2与UO2之间，同时预测(Th, Pa)O2和(U, Pa)O2的带隙也处于ThO2与UO2的带隙值之间. 电子性质计算表明PaO2和UO2是Mott绝缘体，而ThO2是电荷转移绝缘体，这些是和实验和理论结论是一致的. 而(Th, Pa)O2和(U, Pa)O2在费米能级附近的电子态有显著的自旋极化效应，且导带分别主要是Pa-5f和U-5f电子态占据. 最后，对比分析了这些体系的光学介电函数的实部和虚部以及光学参数.

Abstract:

Based on the first-principles of density functional theory, we use the PBEsol + U method to calculate the lattice and electronic structures, as well as mechanical and optical properties of ThO2, PaO2 and UO2 and (Th, Pa)O2 and (U, Pa)O2. The results of structural optimization indicate that the PBEsol + U method can provide more accurate lattice and mechanical parameters for actinide-based oxide ThO2, PaO2, and UO2. The calculation results show that the lattice parameters and the bandgaps of ThO2, PaO2, and UO2 are consistent with the experimental values and other related theoretical values. In the meanwhile, the lattice parameters of (Th, Pa)O2 and (U, Pa)O2 are between ThO2 and UO2, while predicting the band gaps of (Th, Pa)O2 and (U, Pa) O2 are also between ThO2 and UO2. Electronic properties calculations indicate that PaO2 and UO2 are Mott insulators, while ThO2 is a charge-transfer insulator. These are consistent with experiments and theoretical conclusions. (Th, Pa)O2 and (U, Pa)O2 have significant spin polarization effects near the Fermi energy level, and the bands are mainly occupied by Pa-5f and U-5f electronic state, respectively. Lastly, the real and imaginary parts and optical parameters of the optical dielectric functions of these systems are compared and analyzed.