Effective Interaction Strength in Liquid Mixtures: Weighting Interaction Potentials with an Effective Occurrence Factor

The thermodynamics of mixing and demixing of molecular liquids poses a perpetual challenge for atomistic simulations. We provide a compu-tational tool, the effective interaction strength, which can be used to quantify the enthalpic contribution of individual species-dependent inter- actions. The effective interaction strength is configuration-dependent and thus reflects how the actual simulated state (i.e., mixed or phase separated) affects the average particle interactions. Beyond that, the effective interaction strength can be utilized to gain atomistic insight into complex phenomena, including the fundamental nature of the philicity of a compound and the contributions of individual functional groups to this philicity.