Assessing factors that determine adatom migration and clustering on a thin film oxide; Pt1 and Rh1 on the “29” CuxO/Cu(1 1 1) surface

•The distribution of Rh species on the "29" oxide is heterogeneous while it is uniform for Pt.•The relative interaction strengths toward Cu and O determine adatom mobility.•Adatom mobility is proportional to the energy cost to distort the oxide layer.•Cohesion between metals and shallow potential energy surface expedite clustering.