Acta Phys. -Chim. Sin. ›› 2015, Vol. 31 ›› Issue (Suppl): 75-80.

• ARTICLE •

### An Electronic Structure Calculation for 5f States of δ Phase Plutonium Based on the Density Functional Theory Method

LI Ru-Song1, HE Bin1, LI Gang1, XU Peng1, LU Xin-Cheng2, WANG Fei1

1. 1 Xi'an Research Institute of High Technology, Xi'an 710025, P. R. China;
2 Navy Research Institute of Nuclear and Chemistry Safety, Beijing 100077, P. R. China
• Published:2015-05-20
• Contact: LI Ru-Song E-mail:rusong231@126.com
• Supported by:

The project was supported by the National Natural Science Foundation of China (51401237, 51271198, 11474358) and Self-Topics Fund of Xi'an Research Institute of High Technology under Contract, China (2014QNJJ018, YX2012cxpy06).

Abstract:

First-principle calculations of 5fn (n=0-7) electronic configurations are performed with several density functional theory (DFT) methods to describe the localized/delocalized states and obtain the precise population of the 5f manifold in delta-plutonium (δ-Pu). The results show that spin polarization clearly reduces the cohesive energies of each electronic configuration, and enhances the cohesion properties. For 5f0, 5f1, 5f3, 5f4, and 5f6 electronic configurations, the cohesive energies obtained by the spin- polarized local density approximation (SP-LDA)+U method are markedly smaller than that by the SP-LDA method when the lattice constant of δ-Pu exceeds 0.475 nm. The cohesive energies calculated with the spin-polarized generalized gradient approximation (SP-GGA)+U method are smaller than that by SP-GGAmethod, except for 5f4 and 5f6 electronic configurations, and the former trend to coincide with SP-LDA results when the lattice constants are larger than 0.570 nm. For the SP-LDA(GGA)+Umethod, the cohesive energies of 5f0, 5f1, 5f3, 5f4, and 5f6 (5f0, 5f1, 5f2, 5f3, 5f5, and 5f7) electronic configurations are all equal, while the cohesive energies of 5f2, 5f5 (5f4) electronic configurations are the same as that of the 5f7 (5f6) electronic configuration. The cohesive energies of 5fn electronic configurations calculated using the other methods are equal. 5f projected densities of states show that spin polarization results in the exchange split behavior of 5f orbitals. Several 5f states are removed from the Fermi level, which lowers the contribution of 5f states to chemical bonding, and enhances the lattice constant, indicating that strong spin polarization induces partial localization of 5f orbitals. The optimized lattice constants obtained by the SP-LDA method are in good agreement with the experimental values, but the SP-GGA+U method sharply overestimates the lattice constant (by up to about 20%).

MSC2000:

• O641