%V 92 %N 13 %J PHYS REV LETT %T Water dimer diffusion on Pd{111} assisted by an H-bond donor-acceptor tunneling exchange %L discovery91473 %A VA Ranea %A A Michaelides %A R Ramirez %A PL de Andres %A JA Verges %A DA King %K SURFACES, RU(0001) %X Based on the results of density functional theory calculations, a novel mechanism for the diffusion of water dimers on metal surfaces is proposed, which relies on the ability of H bonds to rearrange through quantum tunneling. The mechanism involves quasifree rotation of the dimer and exchange of H-bond donor and acceptor molecules. At appropriate temperatures, water dimers diffuse more rapidly than water monomers, thus providing a physical explanation for the experimentally measured high diffusivity of water dimers on Pd{111} [Mitsui et al., Science 297, 1850 (2002)]. %D 2004 %O © 2004 The American Physical Society %I AMERICAN PHYSICAL SOC