Home – Home – Jornals – Journal of Structural Chemistry 2010 number 1

Using a fully relativistic DV cluster method, we study the electronic structure of a large fragment of the crystal lattice of zircon ZrSiO₄ with a plutonium dopant atom replacing a Zr⁴⁺ zirconium atom. Three possible states of the impurity center are considered: Pu⁴⁺ (isovalent substitution), Pu³⁺ (non-isovalent substitution), and Pu³⁺ with an oxygen vacancy in the nearest environment that provides charge compensation. Relaxation of the ZrSiO₄ 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 Pu³⁺ impurity. In the presence of vacancies the structure of chemical bonding is intermediate with respect to substitutions Pu⁴⁺ → Zr⁴⁺ and Pu³⁺ → Zr⁴⁺.