Does Water Adsorb Molecularly or Dissociatively on a Plutonium Surface?

DFT-GGA has been used to study adsorption of water in molecular and dissociative configurations on $\delta $-Pu (111) surface. In molecular state, water is physisorbed in an almost flat-lying orientation at a one-fold coordinated on-top site. The interaction of the water 1$b_{1}$ orbital and the Pu-6$d$ orbital provides the stability of water on the surface, implying that the Pu-5$f$ electrons remain chemically inert. The coadsorption cases of partially dissociated and fully dissociated products at the three-fold hollow sites yield chemisorption, coupled with rumpling of the surface layer and delocalization of the Pu-5$f$ electrons and formation of strong ionic bonds.