The effect of hydrostatic strain and of interstitial hydrogen on the elastic properties of α-iron was investigated using ab initio density-functional theory calculations. It was found that the cubic elastic constants and the polycrystalline elastic moduli to a good approximation decreased linearly with increasing hydrogen concentration. This net strength reduction could be partitioned into a strengthening electronic effect which was overcome by a softening volumetric effect. The calculated hydrogen-dependent elastic constants were used to determine the polycrystalline elastic moduli and anisotropic shear moduli. For the key slip planes in α-iron, [1¯10] and [11¯2], a shear modulus reduction of approximately 1.6%/at%H was found.

Ab initio Study of the Modification of Elastic Properties of α-Iron by Hydrostatic Strain and by Hydrogen Interstitials. D.Psiachos, T.Hammerschmidt, R.Drautz: Acta Materialia, 2011, 59[11], 4255-63