Here R and P denote the collection of positions and momenta of all particles, H 0 is the noninteracting Hamiltonian for the single i th molecule, U 0 is the intramolecular potential energy (containing only bonded terms) and W [{ φ}] is the interaction energy functional, dependent on the densities of the particles { φ}, modeling the intermolecular interactions. We employ the shorthand { φ} = { φℓ } S ℓ=1 for the collection of number densities associated with all S different particle species in the system. This hybrid approach aims to achieve molecular resolution through H 0 and a smooth free energy landscape by adopting a density-dependent interaction energy functional, with minimal steric hindrance. Since H 0 is nothing but a standard molecular mechanics Hamiltonian, in the following we focus on W [{ φ}]. We adopt a variation of the commonly used Flory-Huggins interaction functional: