A universal force field for molecular and electron dynamics

Machine learned force fields are becoming the standard method to expand the simulation size and time scale of quantum mechanical ab initio molecular dynamics simulations. Their accuracy is as good as the methods they are trained with. Yet, while they are reactive force fields, capable of dealing with a certain level of bond breaking and formation, they are non universal. Even more, the electronic degrees of freedom are rarely incorporated. Here we present an electron force field (EFF) approach that addresses this problem by modeling independent electrons within a classical force field framework. In our EFF electrons and nuclei are interacting particles under a charge and spin-dependent force field. Electronic degrees of freedom are modeled by spherical electron balls (e-balls) with variable position and width. We will present results which show how the interplay between nuclear and electronic degrees of freedom in our method provides a novel tool to explore electron-ion dynamics both in the ground and excited states.