Computer Simulations for Hydrogen Loaded Palladium Clusters

摘要: In this work, a new expression for the chemical potential μ of H in Pd is used, which relies on an extension Widom's particle insertion method. Being exact expression, contains term that agrees with configurational entropy ideal solution model, and describes energy gain system when adding extra atom. This latter due to direct hydrogen-hydrogen interactions, deformations lattice by absorbed hydrogen atoms, from relaxation binding E Pd. The calculation carried out bulk 923 Pd-atoms cuboctahedral cluster within hybrid monte carlo - molecular dynamics (MC-MD) procedure. Also determined as function concentration x cluster. order perform calculations set interaction potentials are applied describe Pd-Pd, H-Pd H-H interactions. For Pd-Pd several models were tested, include first, second or third shell neighbours. first neighbour model. next model nearest used. chosen equilibrium constant pure was constructed reproduce elastic properties atoms metal its relationship relative volume change under loading, also at dilute concentrations. appearance two phase region PdH bulk. Binding 1 atom test sites surface Energies found different surface-like bulk-like sites, agreement experimental results. shows no directional dependence, but one follows geometry system. x, low concentrations, qualitative good discrepancy higher concentrations missing electronic band structure effects very strong repulsive interactions not taken into account. reproduces It that, ppI-HH**-HPdmod, it possible 300 K. presence α-α' transition established. cluster, K, calculated. identify transition. Sievert's law limit estimated experiment, both shifted compared experiments. Using Maxwell construction, solubility limits Also, prediction lattice-Green's formalism, our results demonstrates (NN) (100) configuration show rather attractive mediated interaction, while (N) pairs (110) have coupling. predicts α-phase regime moderate temperatures chain-like distributions shall be preferred structure.