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Evaluating charge equilibration methods to generate electrostatic fields in nanoporous materials

Daniele Ongari1*, Peter G. Boyd1, Ozge Kadioglu2, Amber K. Mace1, Seda Keskin2, Berend Smit1*

1 Laboratory of Molecular Simulation, Institut des Sciences et Ingénierie Chimiques, Ecole Polytechnique Fédérale de Lausanne (EPFL), Rue de l’Industrie 17, CH-1951 Sion, Valais, Switzerland

2 Department of Chemical and Biological Engineering, Koc University, Rumelifeneri Yolu, Sariyer, 34450 Istanbul, Turkey

* Corresponding authors emails: daniele.ongari@epfl.ch, berend.smit@epfl.ch
DOI10.24435/materialscloud:2018.0017/v2 [version v2]

Publication date: Nov 29, 2018

How to cite this record

Daniele Ongari, Peter G. Boyd, Ozge Kadioglu, Amber K. Mace, Seda Keskin, Berend Smit, Evaluating charge equilibration methods to generate electrostatic fields in nanoporous materials, Materials Cloud Archive 2018.0017/v2 (2018), doi: 10.24435/materialscloud:2018.0017/v2.


Charge equilibration (Qeq) methods can estimate the electrostatic potential of molecules and periodic frameworks by assigning point charges to each atom, using only a small fraction of the resources needed to compute density functional (DFT)-derived charges. This makes possible, for example, the computational screening of thousands of microporous structures to assess their performance for the adsorption of polar molecules. Recently, different variants of the original Qeq scheme were proposed to improve the quality of the computed point charges. One focus of this research was to improve the gas adsorption predictions in Metal Organic Frameworks (MOFs), for which many different structures are available. In this work, we review the evolution of the method from the original Qeq scheme, understanding the role of the different modifications on the final output. We evaluated the result of combining different protocols and set of parameters, by comparing the Qeq charges with high quality DFT-derived DDEC charges for 2338 MOF structures. We focused on the systematic errors that are attributable to specific atom types to quantify the final precision that one can expect from Qeq methods in the context of gas adsorption where the electrostatic potential plays a significant role, namely CO2 and H2S adsorption. In conclusion, both the type of algorithm and the input parameters have a large impact on the resulting charges and we draw some guidelines to help the user to choose the proper combination of the two for obtaining a meaningful set of charges. We show that, considering this set of MOFs, the accuracy of the original Qeq scheme is often still comparable with the most recent variants, even if it clearly fails in the presence of certain atom types, such as alkali metals. Version 2 of the record adds the data underlying the figures in CSV format.

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39.7 MiB Inputs for Qeq methods, adsorption results and charge comparison by atom type.


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partial charges Qeq charge equilibration methods MARVEL