Atomistic Modeling of H absorption in Pd nanoparticles

E. CRESPO; M. RUDA; S. RAMOS DE DEBIAGGI

Buenos Aires

Congreso; 15th. Internacional Symposium on Metastable, Amorphous and Nanostructured Materials; 2008

Understanding   the process   of absorption and desorption of H in metals is important in the design of new materials apt for safe H storage. In the case of Palladium, a very strong H absorber, this property has also been used for other important   applications such as catalysts for a number of industrial reactions. In this work we analyze the effect of the size of nano-particles on the properties of absorption of H in Palladium. Because of the higher proportion of surface atoms in nanoparticles compared with the bulk, the pressure-composition (P-C) isotherms of the nanoparticles are modified with respect to the corresponding bulk ones. We made atomistic simulations of Pd nanoparticles with H in at different concentrations. We performed Monte Carlo simulations in the TPmN ensamble to calculate the P-C  isotherms. We used potentials of the Embedded Atom (EAM) type to describe the Pd-H interaction. We considered the potentials recently developed Pd-H EAM potentials which describe, in a satisfactory way, the Pd-H interaction up to higher H concentrations than other potentials available in the literature.  Previous simulations results show that H is absorbed primarily in the surface before diffusing into the inside of small Pd clusters. In this work we show the predictions of Zhou?s potentials regarding the evolution of the equilibrium microstructure of Pd nanoparticles as a function of their size and H concentration.