Density functional theory was used to investigate vacancies at or below the (111) surface of Pd and in the bulk. An accurate non-local pseudopotential for Pd based on relativistic all-electron calculations was employed. The interaction of the vacancy, a point defect, with a surface, a planar defect, was investigated. Also studied was the interaction between electronic structure and lattice structure around the vacancy. The vacancy-formation energy increased with the depth of the vacancy and with decreasing vacancy concentration. The ions surrounding a vacancy relax slightly into it, and the amount of relaxation decreased as vacancy depth was increased or as vacancy concentration was decreased. The primary electronic effects of the vacancy were a spill-out of electrons into it and a strengthening of the bonds between the neighboring atoms that accompanies the inward relaxation.

Vacancies Below the (111) Surface of Pd. R.P.Kauffman, A.M.Rappe: Physical Review B, 2003, 67[8], 085403 (6pp)