Investigation of the (√3 × √3)R30°-Cu2Si/Cu(1 1 1) surface alloy using DFT

► Evident and surprising similarities between the Si-Cu interaction for each of these phases, despite differences in the surface-2nd layer registry and proven Si-Cu interactions between these two layers. ► Si states in these systems do not undergo significant hybridization, and the Si-Cu bonds lack directionality and form either covalent or metallic states. ► Significant distortions in the 2nd layer Cu 3d orbitals which are exactly compensated by bond length differences between the surface and 2nd layer, suggesting the masking of these effects in a simple work function analysis. ► Preliminary energetic analysis suggestive that boundary and mass transport effects dominate the formation of the stable mixed phase surface.