Assigning atomic partial charges is necessary to accurately describe the electrostatic contributions in classical force-fields, but existing methods are either too computationally expensive or do not fully account for variations in the charges due to the local chemical environment. Recently, Wilmer et al. introduced an extended charge equilibration (EQeq) scheme for obtaining atomic partial charges based on using measured ionization potentials and electron affinities of atoms [J. Phys. Chem. Lett. 2012  , 3, 2506-2511]. However, EQeq erroneously predicts constant (environment independent) charges for high oxidation state transition metals in amine templated metal oxide (ATMO) compounds, contrary to the variation observed in iterative Hirshfeld (Hirshfeld-I) charges, bond-valence sum calculations, and formal oxidation state calculations.To fix this problem, we present a simple, non-iterative empirical pairwise correction based on the Pauling bond-order/distance relationship, which we denote EQeq+C. We parameterized the corrections to reproduce the Hirshfeld-I charges of ATMO compounds, and REPEAT charges of metal organic framework (MOF) compounds. The EQeq+C correction fixes the metal charge problem, and significantly improves the partial atomic charges compared to EQeq. We demonstrate the transferability of the parameterization by applying it to a set of unrelated biological molecules. The EQeq+C correction requires minimal computational overhead, making it suitable for treating large unit cell solids and performing large-scale computational screening of materials for a variety of applications including inorganic solids, biological molecules, and metal organic frameworks.

EQeq+C: An empirical bond-order corrected extended charge equilibration method

248th National Meeting (2014)

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