Structures of UO2 and PuO2 surfaces with hydroxide coverage

Atomic scale computer simulation is used to predict the energies and structures associated with surface hydroxide groups on the (1 0 0), (1 1 0) and (1 1 1) surfaces of UO2 and PuO2. The (1 0 0) surface is of particular interest since it is dipolar and therefore must be stabilised by a series of surface defects. Two different (1 0 0) defect terminations are considered, one a conventional series of surface layer defects, the other a partial reconstruction with (1 1 1) like facets. The latter is the most stable termination in the absence of hydroxide. In the presence of hydroxide this preference is reversed.