Electronic structure of Pu3+ and Pu4+ impurity centers in zircon

• Published in: Journal of structural chemistry 2010-02, Vol.51 (1), p.1-8
• Main Authors: Ryzhkov, M. V., Ivanovskii, A. L., Porotnikov, A. V., Shchapova, Yu. V., Votyakov, S. L.
• Format: Article
• Language: English
• Subjects: Atomic; Atomic/Molecular Structure and Spectra; Chemistry; Chemistry and Materials Science; Inorganic Chemistry; Molecular; Optical and Plasma Physics; Physical Chemistry; Solid State Physics
• ISSN: 0022-4766; 1573-8779
• DOI: 10.1007/s10947-010-0001-7

Using a fully relativistic DV cluster method, we study the electronic structure of a large fragment of the crystal lattice of zircon ZrSiO 4 with a plutonium dopant atom replacing a Zr 4+ zirconium atom. Three possible states of the impurity center are considered: Pu 4+ (isovalent substitution), Pu 3+ (non-isovalent substitution), and Pu 3+ with an oxygen vacancy in the nearest environment that provides charge compensation. Relaxation of the ZrSiO 4 crystal lattice near a defect is simulated using a semi-empirical method of atomic pair potentials (GULP program). An analysis of overlap populations and effective charges on atoms shows that the chemical bonding of plutonium with a matrix is covalent, while isovalent substitution yields a more stable system than a Pu 3+ impurity. In the presence of vacancies the structure of chemical bonding is intermediate with respect to substitutions Pu 4+ → Zr 4+ and Pu 3+ → Zr 4+ .