Traditional approaches to the construction of atomistic force fields for dynamical simulation utilize energy decomposition schemes as their starting point. This strategy has had considerable success across diverse chemical and materials contexts by virtue of careful tailoring of component energy terms to specific problem domains. This is exemplified by the radically different functional forms used to treat proteins, alloys, semiconductors, and liquids such as water. All of these forms have limitations in terms of their ability to accurately treat charge transfer, avoid double-counting or undercounting of energetic contributions, and support a natural mechanism for effecting bond formation and breaking. We describe a novel approach to force field design based on <i>dressed atom</i> components, by analogy with the virtual excitations of electronic structure theory. Individual dressed atoms are constructed from a statistical ensemble of isolated atom basis densities---the electron density distributions of neutral, ionic, and excited states of a given atom. The statistical ensemble weights that define the dressed atom are constrained to be identical to the statistical ensemble weights for the energy terms contributed by that atom to the force field, and these weights vary as a function of the evolving local environment, based on chemical potential equalization. We show how this simple yet intuitive picture provides a unifying perspective for the construction of a single force field framework applicable to molecules, biophysical systems, and materials, and discuss initial parameterization strategies for simple molecular systems.

Dressed atom design of charge-transfer force fields

254th National Meeting (2017)

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