Ab Initio Thermodynamics of Surface Oxide Structures under Controlled Growth Conditions

Having a robust and predictive ab initio thermodynamic model to examine and describe the interplay of the oxygen gas and evaporated metal atoms on another metal substrate may prove to be very helpful in understanding the surface phase diagrams of these oxygen/metal systems. In this work, we examine the O/Cu/Au(111) system and provide a refined atomistic thermodynamic model which takes different definitions of the chemical potential of the less abundant metal, Cu into account. We argue that the latter highly depends on the various surface structures (overlayers and alloys) that forms on the metal substrate under growth conditions. We demonstrate that our improved thermodynamic model rationalizes new experimentally observed oxide structures and may pave a systematic way to predict new surface structures of reduced stoichiometries, which would otherwise be missed by the common practice of taking only the bulk limits.