Lattice distortions and relaxation energies due to hydrogen in FCC and BCC metals

Abstract

The lattice distortions and elastic relaxation energies due to interstitial hydrogen defects in metals are calculated from the method of lattice statics. Experimental values of the change in volume, Delta V, due to the defect are used to determine the hydrogen-metal forces. Calculations are performed for tetrahedral and octahedral interstitials in Pd, Ni, Nb, V and Ta for a model in which only nearest-neighbour hydrogen-metal forces are considered. Estimates for a number of other metals in which Delta V is not known are made by assuming Delta V=2.9 AA³. Nearest-neighbour distortions of metal atoms are found to be approximately 1% of the metal lattice parameter and relaxation energies are calculated to be around -0.1 eV except for the alkali metals for which the estimated relaxation energies are of the order of -0.001 eV.