III International Conference

PP-I-79Adsorbing hydrogen and oxygen atoms can occupy following states: two threefoldhollow sites, namely the fcc and hcp, twofold bridge site and on-top. Computed frequency ofsymmetrical valence vibrations occurring perpendicular to the surface heavily depends on thenumber of metal atoms coordinating with the atom. Vibration frequency dramaticallyincreases with decreasing of number of bonds in adsorption center.Table 1. Computed adsorption energies (E ads ), zero point energy effects have been included,equilibrium heights (r 0 ) above the surface, vibration frequencies (ν) of adsorbed H and Oatoms (θ = 1 ML) for following adsorption sites on Pt(100) and Pt(111).H/Pt(111)Site E ads , ev/atom r 0 , Å ν, cm -1on-topbridgehcpfccfcc*hcp*- 0.99-1.36-1.48-1.54-0.99-0.501.61.151.01.0-1.1-0.620221318129012817521102H/Pt(100)on-topbridgehollow-0.88-1.42-1.621.61.10.520271359710O/Pt(111)on-topbridgefcchcp-1.41-1.47-1.73-1.221.81.41.21.25772642564611Threefold hollow sites (fcc and hcp) for adsorption of H and O atoms are preferredcompared to weakly-bond energy sites (on-top or bridge). It is shown that hydrogen atomscan occupy subsurface sites (fcc* and hcp*). So we considered OH-groups adsorbed onPt(100) and Pt(111) on-top and bent configurations.The financial support of RFBR № 05-03-32971 and Zamaraev Foundation is highlyappreciated.149