Atomic structure and electronic state of <110> symmetric tilt boundaries in palladium

In this study, the energy and atomic structure of the < 110 > symmetric tilt boundaries in palladium were calculated using a molecular dynamics (MD) method and the electronic structures of hydrogen in the bulk and at the grain boundaries were calculated using discrete-variational X alpha (DV-X alpha) molecular orbital cluster calculaion by solving Hartree-Fock-Slater equation. The result of MD simulation revealed that the energy of the < 110 > symmetric tilt boundary of palladium depended on the misorientation angle and that there were large energy cusps at the misorientation angles which correspond to the {111} and 1113 ill symmetric tilt boundaries. The atomic structure of all < 110 > symmetric tilt boundaries could consist of the combination of the {331} Sigma 19, {111}Sigma 3 and {113}Sigma 11 structural units and {110}Sigma 1 and {001}Sigma 1 single crystal units. The result of DV-X alpha molecular orbital cluster calculation showed that the interstitial hydrogen atoms induced the palladium-hydrogen chemical bond which had a different energy level from the palladium-palladium bond. The component of the palladium-hydrogen bond at the grain boundaries was similar to those in the bulk palladium. It is clarified that electronic structure near the grain boundary is different from that in the perfect crystal.