Atomistic molecular dynamics simulations have become an indispensable part of modern day theoretical chemistry. The development of classical, fixed charge force fields (FFs) they typically employ has been ongoing for 35 years. However, non-ideal parameters and the approximate nature of FFs is still a key source of error in molecular simulations.<br/>In additive FFs, electrostatics is approximated between point charges centered at atoms interacting via a Coulomb potential. These atomic charges are usually derived by methods based on QM electrostatic potentials, like RESP and AM1-BCC. These methods, developed 20 years ago, still rely on the computational power and methods of those days. We will present a new parameterization scheme based on more accurate QM data, allowing us to reproduce experimental properties more accurately. The presented method achieves these improved results by allowing the FF polarity to be tuned against experimental training data.<br/>Even with optimal point charges, the precision of fixed charge FFs would be limited by their neglect of polarization effects, which means that the electrostatic model of a molecule does not adapt to changes in the molecule’s environment. Polarizable force fields (PFFs) include polarization explicitly, making them physically more complete. Nevertheless, they are not yet outperforming classical FFs. The two major drawbacks, responsible for the slow spread of PFFs for scientific applications, are their high computational costs and the lack of adequate parameterization schemes. We will describe a strategy, consistent with our fixed charge model, to develop and reparametrize computationally efficient, well defined, charge and polarizability parameters for molecular simulations. The accuracy of the developed electrostatics models is evaluated based on their ability to reproduce quantum chemical electrostatic potentials. Additionally, we show how one set of polarizability parameters can be used with different charge models, without significant loss of accuracy, making the parameterization of future polarizable force fields easier.

Advanced electrostatic potential based methods to derive atomic charges and polarizabilities

2019 Fall National Meeting

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