Reference Depolarization Values for Polar-Organic Aggregates

A key aspect in the design of mixed polar-organic layers and metallic or semiconducting devices is the dielectric constant of the organic aggregate, which modulates the surface work function and band alignments. In simple electrostatic models, a monolayer is treated as an array of point dipoles whose depolarization depends only on an effective molecular polarizability. However, the absence of a unified framework in quantum-chemical computational studies leaves the reliability of the point dipole model uncertain. In this work, we demonstrate the breakdown of the point dipole approximation for highly packed aggregates and propose an alternative heuristic model that relies on a second molecular parameter: the molecular size. The performance of this approach is validated through comparison with computational methods based on Density Functional Theory (DFT) and second-order Møller-Plesset perturbation theory (MP2) calculations. Our extended dipole model provides robust estimates of depolarization effects, offering a rapid prescreening tool for selecting polar organic candidates in surface functionalization.