AbstractAb initio SCF‐CI theory has been used to examine the interactions of a single water molecule with a 31‐atom nanocluster of palladium. Calculations are performed on singly‐charged cationic and anionic particles in addition to the neutral system to determine effects of charging on the adsorption energy of water and the barriers to dissociation. Penetration of the dissociated H through the surface layer into an interstitial subsurface site is also examined. Adsorption energies of an intact water molecule fall in the range 0.2–0.8 eV, while the barrier to dissociation into a subsurface site is in the range 1.4–2.1 eV depending on the charge of the metal particle. Calculations on the photoinduced dissociation of water adsorbed on the Pd surface are also reported, and dissociation pathways with smaller energy barriers than found for the ground state are shown to exist. © 2010 Wiley Periodicals, Inc. Int J Quantum Chem, 2010