provides an insight into whether further refinement of force field parameters may yield improved quality-of-fits to the structure. In this instance, the experimental target exceeds the σ noise ∼ 0.005 precision threshold recommended for direct force field optimization to neutron scattering data, suggesting that additional experimental targets would be beneficial for further optimizing TMApyridine force fields. Even though prosECCo75 and CHARMM36 differ only in their treatment of charged species, the simulations of the TMACl-pyridine system reveal stark contrasts in structural behavior of the two force fields. To explore these differences, we calculated density maps from the simulations to visualize the geometric preferences of these interactions. Specifically, the maps represent the spatial density of TMA carbons around the atoms of the six-membered aromatic ring. The density map calculated from the trajectory using CHARMM36 FF (Fig. ) exhibits a headphone-like distribution, where the density wraps around the electronegative atom of the aromatic molecule.