Incorporating Complex Pair Potentials Into Field-theoretic Simulations

Field-theoretic simulations (FTS) are a powerful tool for studying the structure and thermodynamics of polymeric materials. One limitation of FTS is that they have historically been constrained to simplistic pair potentials that are considerably less expressive that those employed in particle-based simulations (e.g., Lennard–Jones). In this work, we surmount this limitation by extending a framework recently proposed by Fredrickson and Delaney¹ where pair potentials of arbitrary complexity are constructed using a Gaussian basis set. Using this framework, we demonstrate that physically realistic attraction–repulsion pair potentials can be performed using FTS. We analyze this framework using both the random phase approximation and complex Langevin simulations and validate that the pressure, chemical potential, and structure factor are consistent with molecular dynamics simulations of the same model. Our work also examines the vapor-liquid phase diagrams that emerge from pair potentials with both single and multiple attractive minima. This work demonstrates that FTS can be extended beyond simplistic pair potentials and can be used to study systems with complex short-ranged molecular interactions.