Surface Structure ofα-Ga(010)

We have determined the surface structure of $\alpha$- $\mathrm{Ga}\left(010\right)$ near its melting point using x-ray diffraction. Of the two possible ideal ways to form the $\left(010\right)$ surface, we find that the true surface is formed by cutting through dimer bonds (i.e., between metallic bilayers). The contraction of the metallic bonds and the expansion of the covalent bonds at the surface imply that the surface is more metallic than the bulk. Our results suggest that $\alpha$-Ga is fundamentally composed not of ${\mathrm{Ga}}_2$ dimers, but of corrugated metallic bilayers which can be modeled as deltahedral clusters.