Ewald Electrostatics for Mixtures of Point and Continuous Line Charges

Many charged macro- or supramolecular systems, such as DNA, are approximately rod-shaped and, to the lowest order, may be treated as continuous line charges. However, the standard method used to calculate electrostatics in molecular simulation, the Ewald summation, is designed to treat systems of po...

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Bibliographic Details
Published in:The journal of physical chemistry. B 2015-10, Vol.119 (41), p.13218-13226
Main Authors: Antila, Hanne S, Tassel, Paul R. Van, Sammalkorpi, Maria
Format: Article
Language:English
Subjects:
Charge
Deviation
Discretization
Electrostatics
Equivalence
Mathematical analysis
Mathematical models
Models, Theoretical
Separation
Static Electricity
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Summary:Many charged macro- or supramolecular systems, such as DNA, are approximately rod-shaped and, to the lowest order, may be treated as continuous line charges. However, the standard method used to calculate electrostatics in molecular simulation, the Ewald summation, is designed to treat systems of point charges. We extend the Ewald concept to a hybrid system containing both point charges and continuous line charges. We find the calculated force between a point charge and (i) a continuous line charge and (ii) a discrete line charge consisting of uniformly spaced point charges to be numerically equivalent when the separation greatly exceeds the discretization length. At shorter separations, discretization induces deviations in the force and energy, and point charge–point charge correlation effects. Because significant computational savings are also possible, the continuous line charge Ewald method presented here offers the possibility of accurate and efficient electrostatic calculations.
ISSN:1520-6106
1520-5207
DOI:10.1021/acs.jpcb.5b07637