RANGE OF FORCES ON HOST-METAL ATOMS AROUND INTERSTITIAL HYDROGEN IN PD AND NB

Forces on the host-metal atoms surrounding a hydrogen atom at differen t interstitial positions in palladium and niobium are calculated from first principles in the local-density approximation with a mixed-basis pseudopotential supercell approach. For supercells Pd(n)H (n = 1,4,8, 16,32) previously reported results are reanalyzed and corrected based on a recently noticed simplification in the computational method. Resu lts are presented for supercells Nb(n)H (n = 1,2,4,8,16). In both elem ents the displacement forces decay dominantly within the range of one lattice constant. The elastic force-dipole tensors are determined from the first-principles forces. The results for octahedral occupation of H in Pd and tetrahedral occupation of H in Nb support the picture of static occupation of distinct interstitial sites.