Adsorption and dissociation of water on the (0001) surface of double hexagonal close packed americium

Ab initio total energy calculations within the framework of density functional theory have been performed for water molecule adsorption on the (0001) surface of double hexagonal packed americium using a full‐potential all‐electron linearized augmented plane wave plus local orbitals method (FP‐L/APW + lo). Subsequent partial dissociation (OH + H) and complete dissociation (H + O + H) of the water molecule have been examined. The completely dissociated H + O + H configuration exhibit the strongest binding with the surface (3.35 eV), followed by partially dissociated species OH + H (2.23 eV), with all molecular H 2 O configurations showing weak physisorption (0.366 eV). For molecular adsorptions, the flat lying orientation of the water molecule if found to be more favorable for majority of the cases. In the case of partial dissociation (OH + H), the vertical orientation of OH molecule with O facing the surface adsorbed at a h3 adsorption site and the H atom adsorbed at another neighboring h3 site is found to be the most favorable. For complete dissociation (H + O + H), the dissociated species occupy three different neighboring h3 adsorption sites. The changes in work functions and net magnetic moments are presented for all the cases studied. The adsorbate‐substrate interactions have been analyzed in detail using difference charge density distributions and the local density of states. The effects of adsorption on the Am 5f electron localization‐delocalization characteristics have been discussed. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)