Electronic structure and chemical bonding properties of UO2F2 from first principles

Band theoretical results are presented on UO2F2 equi-oxyfluoride based on computation methods within the density functional theory. From pseudo-potential projector augmented wave PP–PAW calculations the equation of state is obtained with equilibrium properties in agreement with experiment. For isotropic volume change a bulk modulus of B0 = 150 GPa indicates a relatively soft material but anisotropic compression along the c-axis leads to excessive hardness. Scalar-relativistic all-electron calculations detailing the band structure point to little dispersion of the bands with a large band gap of ∼3.2 eV. It is direct at Γ and occurs between highest occupied valence band (VB) [U(fz3)–O(p)][U(fz3)–O(p)] and lowest unoccupied conduction band [U(fx,y)]. Analyses of the density of states (PDOS) and chemical bonding properties show that the VB lower part is dominated by U(d)–F(p) bonding while the VB upper part comprises U(f)–O(p) strong covalent interactions. These results provide a band structure illustration of the complex uranyl cation UO22+.

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