A theoretical study of H absorption at a Fe(110)-Pd(100) Interface and Fe-Pd alloys

ESTELA ANDREA GONZALEZ; PAULA VERÓNICA, JASEN; CASTELLANI NORBERTO,; JUAN ALFREDO,

JOURNAL OF MATERIALS SCIENCE

SPRINGER

Año: 2005 vol. 40 p. 2775 - 2782

0022-2461

The electronic structure and bonding at a Fe(110)-Pd(100) interface was theoretically analyzed in the framework of semi-empirical quantum chemical calculations. The Fe-Pd interface was modeled by a Fe74Pd74 cluster and a Fe-Pd six layer slab.     The extended Hückel tight binding (EHTB) method and its modifications, including repulsive interactions, were used to calculate the interfacial adhesion and the H-absorption energy.     The energetic minimum position for H is found at the Fe-Pd interface closer to the Pd layer.    The interfacial Fe-Pd distance result to be 1.73 Å where Fe-Pd develops a strong bonding interaction. An important metal-metal adhesion was also found.     The changes in the Density of States (DOS) and the Crystal Orbital Overlap Population (COOP) were compared in different structures: clusters, slab and two types of Fe-Pd alloys.     The H as an impurity is responsible for a Fe-Fe and Pd-Pd bond weakening. However, the H effect is much less detrimental for the Fe-Pd bonds at the interface.     When H is located at interstitial sites in bulk Fe-Pd alloys, the Pd-Pd overlap population shows a notorious decrease in the case of fcc structures while for fct structures the change is only 12%. The intermetallic bonding was also weakened as compared with the pure alloys. The objective of this work is to bring a plausible explanation to the null permeability to hydrogen in Pd-coated Fe films.