title: DFT and two-dimensional correlation analysis methods for evaluating the Pu(3+)-Pu(4+) electronic transition of plutonium-doped zircon.
abstract: Understanding how plutonium (Pu) doping affects the crystalline zircon structure is very important for risk management. However, so far, there have been only a very limited number of reports of the quantitative simulation of the effects of the Pu charge and concentration on the phase transition. In this study, we used density functional theory (DFT), virtual crystal approximation (VCA), and two-dimensional correlation analysis (2D-CA) techniques to calculate the origins of the structural and electronic transitions of Zr1-cPucSiO4 over a wide range of Pu doping concentrations (c=0-10mol%). The calculations indicated that the low-angular-momentum Pu-fxy-shell electron excites an inner-shell O-2s(2) orbital to create an oxygen defect (VO-s) below c=2.8mol%. This oxygen defect then captures a low-angular-momentum Zr-5p(6)5s(2) electron to form an sp hybrid orbital, which exhibits a stable phase structure. When c>2.8mol%, each accumulated VO-p defect captures a high-angular-momentum Zr-4dz electron and two Si-pz electrons to create delocalized Si(4+)→Si(2+) charge disproportionation. Therefore, we suggest that the optimal amount of Pu cannot exceed 7.5mol% because of the formation of a mixture of ZrO8 polyhedral and SiO4 tetrahedral phases with the orientation (10-1). This study offers new perspective on the development of highly stable zircon-based solid solution materials.
authors.affiliation: Key Laboratory of Functional Materials and Devices for Special Environments, Chinese Academy of Sciences, Urumqi 830011, Xinjiang, China; Laboratory for Extreme Conditions Matter Properties, South West University of Science and Technology, Mianyang 621010, Sichuan, China. Electronic address: bianliang@ms.xjb.ac.cn.
authors.forename: Liang
authors.initials: L
authors.lastname: Bian
authors.affiliation: Laboratory for Extreme Conditions Matter Properties, South West University of Science and Technology, Mianyang 621010, Sichuan, China.
authors.forename: Fa-qin
authors.initials: FQ
authors.lastname: Dong
authors.affiliation: Laboratory for Extreme Conditions Matter Properties, South West University of Science and Technology, Mianyang 621010, Sichuan, China.
authors.forename: Mian-xin
authors.initials: MX
authors.lastname: Song
authors.affiliation: Department of Geology and Environmental Earth Science, Miami University, Oxford, OH 45056, USA.
authors.forename: Hai-liang
authors.initials: HL
authors.lastname: Dong
authors.affiliation: Key Laboratory of Functional Materials and Devices for Special Environments, Chinese Academy of Sciences, Urumqi 830011, Xinjiang, China.
authors.forename: Wei-Min
authors.initials: WM
authors.lastname: Li
authors.affiliation: Laboratory for Extreme Conditions Matter Properties, South West University of Science and Technology, Mianyang 621010, Sichuan, China.
authors.forename: Tao
authors.initials: T
authors.lastname: Duan
authors.affiliation: Laboratory for Extreme Conditions Matter Properties, South West University of Science and Technology, Mianyang 621010, Sichuan, China.
authors.forename: Jin-bao
authors.initials: JB
authors.lastname: Xu
authors.affiliation: Key Laboratory of Functional Materials and Devices for Special Environments, Chinese Academy of Sciences, Urumqi 830011, Xinjiang, China; Laboratory for Extreme Conditions Matter Properties, South West University of Science and Technology, Mianyang 621010, Sichuan, China.
authors.forename: Xiao-yan
authors.initials: XY
authors.lastname: Zhang
mesh_terms: D003198:Computer Simulation; D004583:Electrons; D008956:Models, Chemical; D011005:Plutonium / Q000737:chemistry*; D017640:Silicates / Q000737:chemistry*; D015040:Zirconium / Q000737:chemistry*
chemical_list: D017640:Silicates; C003784:zircon; D011005:Plutonium; D015040:Zirconium
keywords: Density functional theory; Plutonium; Two-dimensional correlation analysis; Virtual crystal approximation; Zircon