Electronic structure and total energy of interstitial hydrogen in iron: Tight-binding models

An application of the tight-binding approximation is presented for the description of electronic structure and interatomic force in magnetic iron, both pure and containing hydrogen impurities. We assess the simple canonical d-band description in comparison to a nonorthogonal model including s and d bands. The transferability of our models is tested against known properties including the segregation energies of hydrogen to vacancies and to surfaces of iron. In many cases agreement is remarkably good, opening up the way to quantum-mechanical atomistic simulation of the effects of hydrogen on mechanical properties.