3)R30o-Au and (6x6)-Au surfaces

3-Au surface result in top layer Si atoms with an SiAu4 butterfly wing configuration. The structure of a (6x6)-Au phase, whose in-plane top atomic layer positions were previously determined by an electron holography technique [Grozea et al. Surf. Sci. 418, 32 (1998)], is calculated using total energy minimization. The Patterson function for this structure is calculated and is in good agreement with data from an in-plane x-ray diffraction study [Dornisch et al. Phys. Rev. B 44, 11221 (1991)]. Filled and empty state scanning tunneling microscopy (STM) images are calculated for domain walls and the (6x6)-Au structure. The (6x6)-Au phase is 2D chiral and this is evident in computed and actual STM images. The (6x6)-Au and domain wall structures contain the SiAu4 motif with a butterfly wing shape. Chemical bonding within the Si-Au top layers of the √