Structures of [001] twist boundaries in gold. II. Results obtained by x-ray diffraction and computer simulation

Absolute grain-boundary structure factors, ‖$F_b$‖, were measured for a series of [001] twist boundaries in gold by the x-ray-diffraction method described in the preceding paper. The series included the Σ113(θ=7.6°), Σ25(θ=16.3°), Σ13(θ=22.6°), Σ17(θ=28.1°), and Σ5(θ=36.9°) boundaries (θ being the twist angle). The atomistic structures and ‖$F_b$‖’s of these boundaries were also calculated by computer simulation using the embedded-atom model. The calculated atomic relaxations in the boundary cores consisted mainly of rotations around the O lattice elements, in agreement with previous work, and became monotonically weaker as θ increased. A considerable degree of consistency between measured and calculated ‖$F_b$‖’s was obtained for all five boundaries. The calculated results faithfully tracked large measured decreases in ‖$F_b$‖ as θ increased. Considerable consistency was found between measured and calculated sets of ‖$F_b$‖’s for individual boundaries, particularly for Σ113 and Σ25, where the scattering was relatively strong. For the weakly scattering Σ5 boundary, the observed ‖$F_b$‖’s led to a most probable structure with small displacements which closely resembled the calculated structure. For the intermediate Σ13 and Σ17 boundaries, the limited number of measured ‖$F_b$‖’s was reasonably consistent with calculated values. It was therefore concluded that the atomistic boundary structures calculated by the embedded-atom model were essentially correct. The present boundary structures were in quite good agreement with those of Fitzsimmons and Sass for Σ13, but in strong disagreement for Σ5, where their model possessed displacements that were much too large.