Anisotropy of the stress on fcc(110) surfaces

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Abstract
First-principles calculations for Pd(110)-1×1 and Pt(110)-1×1 slabs imply that the surface stress along the close-packed, [11¯0] direction is larger than in the [001] direction, transverse to the surface channels. This agrees with the simple idea that relaxation of the outermost layer separation, at a fcc(110) surface, allows nearest-neighbor bonds with a component transverse to the channels to relax toward their desired length, while the bonds along the channel walls cannot relax their strain without a surface reconstruction. In contrast, an analysis of the surface phonons of Ni(110), based on an empirical fit to the dynamical matrix, comes to the opposite conclusion, i.e., that the stress in the [11¯0] direction is only half that in the [001] direction.