Dynamics of hydrogen in Pr₂Fe₁₇H₄ and Pr₂Fe₁₇H₅

Abstract

We describe a study of the dynamics of hydrogen in Pr 2 Fe 17 H 4 , where isolated hexagons formed by the interstitial tetrahedral (t) sites of the metal lattice are populated by mobile hydrogen atoms. An activation energy of 0.10 eV has been determined for a localized jump process involving the hopping of these hydrogen atoms among adjacent vertices of each hexagon, slightly lower than that for hydrogen hopping in Pr 2 Fe 17 H 5 , where each hexagon is occupied by two hydrogen atoms.