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MM: Fachverband Metall- und Materialphysik

MM 34: SYM Hydrogen in Materials: New Developments II

MM 34.3: Talk

Thursday, February 28, 2008, 12:30–12:50, H 1058

MC-MD simulations of pressure-concentration isotherms for Hydrogen in bulk Palladium and clusters — •Diana Marcano and Helmar Teichler — Institut fuer Materialphysik, Universitaet Goettingen

For nanoscale Pd clusters loaded with H experimental pressure - concentration isotherms resemble those for bulk material, with the main difference of a finite slope instead of the two-phase regime and a narrowing of this region compared to bulk. Regarding this, we here present results from MC-MD studies using for the chemical potential a new calculation scheme, which means an extension of Widom’s particle insertion method. The simulations rely on the Tomanek model with improved H-Pd coupling for properly taking care of lattice deformations and modified H-H interaction including first and second neighbour interactions. For bulk material, the asymmetric two-phase regime is obtained, extending up to 62 % H. The results for a 923 Pd atoms cuboctahedral cluster reflect the variation of site energies in the cluster where the shift to lower H concentrations is related to the interplay between first and second neighbour H-H interactions.