Energetic and entropic considerations for coarse-graining

Molecular dynamics simulations often adopt coarse-grained (CG) models to investigate length- and time-scales that cannot be effectively addressed with atomically detailed models. However, the effective potentials that govern CG models are configuration-dependent free energies with significant entropic contributions that have important consequences for the transferability and thermodynamic properties of CG models. This review summarizes recent work investigating the fundamental origin and practical ramifications of these entropic contributions, as well as their sensitivity to the CG mapping. We first analyze the energetic and entropic components of the many-body potential of mean force. By adopting a simple model for protein fluctuations, we examine how these components vary with the CG representation. We then introduce a “dual potential” approach for addressing these entropic considerations in more complex systems, such as ortho-terphenyl (OTP). We demonstrate that this dual approach not only accurately describes the structure and energetic properties of the underlying atomic model, but also accurately predicts the temperature-dependence of the CG potentials. Furthermore, by considering two different CG representations of OTP, we elucidate how these contributions vary with resolution. In sum, we hope this work will prove useful for improving the transferability and thermodynamic properties of CG models for soft materials.