“…Surpassing 1 kcal mol −1 accuracy requires model improvements that are difficult to generalize Relative free energy methods almost universally utilize fixed-charge MM force fields to model small, organic, drug-like molecules and interactions with their respective receptors and aqueous environments, such as GAFF [13,14], CGenFF [15,16,16], or OPLS [17]. Importantly, these popular class I [18,19] MM force fields have well-characterized drawbacks, in part, because they omit a number of important energetic contributions known to limit their ability to achieve chemical accuracy [7,20,21]. For example, while moving to more complex electrostatics models which include fixed multipoles and polarizable dipoles [22] are promising, the development of polarizable force fields that broadly deliver accuracy gains has proven challenging [23][24][25].…”