Ab initio study of the interaction of H with substitutional solute atoms in α-Fe: Trends across the transition-metal series

The extent of hydrogen embrittlement in steel depends strongly on the H distribution in the microstructure. Alloying elements might serve to detract hydrogen from regions prone to embrittlement and to distribute it within areas where it causes less damage. We present an ab initio study of the interaction of interstitial hydrogen in α-iron with substitutional transition-metal atoms as alloying elements. We find similar trends for the 3d, 4d, and 5d transition metal elements: the elements in the middle of the transition-metal series repel hydrogen while those on the sides tend to attract hydrogen. The trend is in line with the volume change that the transition-metal solute atom exerts on the iron lattice. The interaction energy decreases rapidly with separation distance with a range of approximately 5 Å. We use a simple parametrisation in order to estimate finite-size effects in the ab initio data.

► We determine the interaction energy of H and TM impurities in bcc Fe. ► We perform ab initio calculations for all TM with several distances to H. ► The interaction energy decreases rapidly with TM–H distance. ► The trend across all TM series is repulsion/attraction/repulsion. ► This trend of interaction is in line with the volume change due to the TM atom.