Electronic band structure of CaUO4CaUO4 from first principles

Band theoretical results are presented on calcium uranate, CaUO4CaUO4, based on computations within the density functional theory. From pseudo-potential calculations the equation of state is obtained with equilibrium lattice properties in agreement with experiment. For isotropic volume change the bulk modulus amounts to 180 GPa but a much higher value is found for anisotropic compression along the hexagonal c  -axis. This is assigned to the short U–O distances in linear uranyl polycation. Scalar relativistic all-electron calculations point to a semiconductor with ~3eV band gap. From density of states, chemical bonding and electron localization function ELF, oxygen is found to behave both as ionic and covalent in the coordination sphere of uranium. The results provide an illustration of the peculiar role of uranyl cation UO22+ according to its chemical environment.

Energy versus volume variation for isotropic and anisotropic compressions within CaUO4CaUO4. Fit results with Birch EOS are given in inserts.Figure optionsDownload full-size imageDownload as PowerPoint slide