Structure and phases of the Au(001) surface: X-ray scattering measurements

X-ray diffraction is used to study the phase behavior and structure of the Au(001) surface between 300 K and the triple point. For T>1170 K, the x-ray reflectivity is consistent with a thin, disordered surface film. At 1170 K, there is a reversible transition to an incommensurate, hexagonal overlayer on top of the square substrate. At 970 K, the orientation of the hexagonal layer rotates discontinuously by 0.81^∘{} with no observable change in incommensurability.