ABINITIO PSEUDOPOTENTIAL CALCULATIONS OF TOTAL ENERGIES AND FORCES FOR HYDROGEN IN PALLADIUM

Ground-state properties of palladium-hydrogen systems are investigated in the framework of density functional theory in the local-density approximation. Norm-conserving ab initio pseudopotentials are used to describe the interactions between electrons and ion cores. The crystalline wave functions and the charge densities of the valence electrons are represented by a mixed basis containing plane waves and additionally localized d-like functions for palladium and s-like functions for hydrogen. Total energies are calculated for Pd-H systems with different hydrogen concentrations using Pd(n)H supercells (n = 1,4, 8, 16, 32). We report on the cohesive properties as well as the diffusion potentials and vibrational energies for the interstitial hydrogen. Lattice relaxations are taken into account by calculating atomic forces according to the Hellmann-Feynman theorem and statically relaxing the atomic positions.