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MM: Fachverband Metall- und Materialphysik

MM 49: Hydrogen in Metals

MM 49.1: Vortrag

Freitag, 27. März 2009, 10:15–10:30, IFW D

Universal trends for the solubility of hydrogen in non-magnetic 3d transition metals derived from first principles — •Ugur Aydin, Lars Ismer, Tilmann Hickel, and Jörg Neugebauer — Max-Planck Institut für Eisenforschung

Hydrogen is an omnipresent element in many materials which may cause materials failure (e.g. hydrogen embrittlement) or maybe used for hydrogen storage. Therefore a detailed understanding/prediction of H solubility (energetics) and kinetics in metals is crucial. In order to identify chemical trends for the solubility and mobility of hydrogen in metals we have performed an extensive ab initio study. Since the number of valence electrons was supposed to have a decisive influence on the quantity, the complete set of all 3d transition metals has been studied under comparable conditions (pure elements, no magnetism, identical fcc lattice structure). With respect to the site preference of the hydrogen atom in these metals, we have identified two different classes, with either the octahedral or the tetrahedral interstitial site being preferred. The corresponding H solution enthalpies, calculated for different lattice constants of the host metal, revealed a remarkable universal trend for all elements. The universal curve has a minimum formation energy (i.e. maximum hydrogen solubility) at a critical fcc lattice constant of ≈ 4.6 Å. Analyzing the data we find that the shape of the curve is a consequence of a volume dependent contribution and the specific electronic configuration of the host material. Based on these results we discuss strategies to identify systems with a optimum H solubility.