Structures of uranyl peroxide hydrates: a first-principles study of studtite and metastudtite

The structures of the only known minerals containing peroxide, namely studtite [(UO2)O2(H2O)4] and metastudtite [(UO2)O2(H2O)2], have been investigated using density functional theory. The structure of metastudtite crystallizing in the orthorhombic space group Pnma (Z = 4) is reported for the first time at the atomic level and the computed lattice parameters, a = 8.45, b = 8.72, c = 6.75 Å, demonstrate that the unit cell of metastudtite is larger than previously reported dimensions (Z = 2) derived from experimental X-ray powder diffraction data.