We present a simple molecular model for the self-assembly of alkanethiols on gold. The model, a rigid rod representation of a molecule which is constrained to a given distance from the gold surface, allows direct long-time simulations of large-scale molecular ensembles (104−105 molecules) on desktop workstations. As a result, the model allows for efficient studies of evolution and ordering of, for example, orientational order and domain patterns in a full range of monolayer coverages. The model is parametrized entirely by existing literature on atomic and molecular scale interactions. Extensive simulations of molecular self-assembled monolayer domain formation at optimal (packing commensurate with a gold surface (111) structure) and suboptimal packing are conducted and presented. The results show close correspondence between the model features and the existing, and emerging, picture observed through experimental characterization of self-assembled monolayers on Au(111). This strong experimental validation ...