The energy of interstitial impurities in transition metals: H in Pd

Abstract

The theory of the electron density of states due to an interstitial impurity in a transition metal developed previously (see ibid., vol.7, p.799 (1977)) is used to determine the energy of the impurity at tetrahedral and octahedral sites in FCC transition metals. The contributions to the energy are a bandstructure term due to the perturbed density of electron states, an electrostatic term to include the additional electrostatic interactions and a term arising from electron exchange and correlation. Detailed calculations are performed for the case of hydrogen in palladium and it is found that the octahedral site has lower energy than the tetrahedral site in agreement with experiment. The calculated values of the energy and heat of formation are also found to be in reasonable agreement with experiment. The accuracy of the host metal bandstructure calculation is shown to be significant. It is concluded that the theory should be sufficiently accurate to determine interstitial site energies for other transition metals.