These past decades, the study of the structure and properties of large chemical and biochemical systems have been possible thanks to the intense development of force fields. Indeed, classical force fields have been widely used and validated among the molecular dynamics community. However due to the key role of intermolecular interactions, which represent attractive and repulsive forces, a second class of force fields have been developed to increase the accuracy of the description of intermolecular interactions. Cisneros <i>et al. </i>have proposed and developed the Gaussian Electrostatic Model (GEM) polarizable force field which is based on fitted molecular electronic densities. GEM uses density fitting techniques and Hermite Gaussian auxiliary basis sets in order to reproduce the molecular electronic densities with higher accuracy. However molecular dynamics (MD) simulations have not been feasible for the full GEM potential due to the lack of an explicit analytical form of the gradient of the charge transfer term and cost for the evaluation of the required integrals. Hence previous works have made significant improvements in Ewald-based approaches, and employed approximations to enable the use of some GEM terms in order to conduct MD simulations. An hybrid force field, named GEM*, has then been developed combining the Coulomb and exchange-repulsion terms from GEM and the polarization and modified van der Waals terms from AMOEBA, a polarizable force field already implemented in several MD packages. Commonly, the construction of a water model has been used as the foundation in the process of force fields development. As a result, condensed phase properties of water computed with GEM* shown good agreement in comparison to experimental data at 300 K. Nevertheless, it is important to note that condensed phase properties are mainly due to dispersion forces. Therefore, the aim of this work is to establish a new dispersion formulation for GEM based either on the dispersion equation from SIBFA, a polarizable force field, or the Tkatchenko-Scheffler method. Testing these two methods will allow us to have a better understanding of dispersion forces in order to build the new GEM water model. Thus, this work is the first step to move towards full GEM molecular dynamics simulations. Also, thanks to the recent implementation of the gradients of the SIBFA charge transfer term into a MD package, the next step to include charge transfer in GEM will be straightforward.

Improvement of the GEM polarizable water model: Importance of the dispersion energy

2019 Fall National Meeting

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.