Title: Electronic structure calculations in electrolyte solutions
Subtitle: Methods for neutralization of extended charged interfaces
Authors: Bhandari, Arihant
Anton, Lucian
Dziedzic, Jacek
Peng, Chao
Kramer, Denis 
Skylaris, Chris-Kriton
Language: en
Subject (DDC): DDC::500 Naturwissenschaften und Mathematik::540 Chemie::541 Physikalische Chemie
Issue Date: 2020
Publisher: American Institute of Physics
Document Type: Article
Journal / Series / Working Paper (HSU): The journal of chemical physics : JCP 
Volume: 153
Issue: 12
Page Start: 124101-1
Page End: 124101-12
Pages: insges. 12 S.
Publisher Place: Melville, NY
Density functional theory (DFT) is often used for simulating extended materials such as infinite crystals or surfaces, under periodic boundary conditions (PBCs). In such calculations, when the simulation cell has non-zero charge, electrical neutrality has to be imposed, and this is often done via a uniform background charge of opposite sign ("jellium"). This artificial neutralization does not occur in reality, where a different mechanism is followed as in the example of a charged electrode in electrolyte solution, where the surrounding electrolyte screens the local charge at the interface. The neutralizing effect of the surrounding electrolyte can be incorporated within a hybrid quantum-continuum model based on a modified Poisson-Boltzmann equation, where the concentrations of electrolyte ions are modified to achieve electroneutrality. Among the infinite possible ways of modifying the electrolyte charge, we propose here a physically optimal solution, which minimizes the deviation of concentrations of electrolyte ions from those in open boundary conditions (OBCs). This principle of correspondence of PBCs with OBCs leads to the correct concentration profiles of electrolyte ions, and electroneutrality within the simulation cell and in the bulk electrolyte is maintained simultaneously, as observed in experiments. This approach, which we call the Neutralization by Electrolyte Concentration Shift (NECS), is implemented in our electrolyte model in the Order-N Electronic Total Energy Package (ONETEP) linear-scaling DFT code, which makes use of a bespoke highly parallel Poisson-Boltzmann solver, DL_MG. We further propose another neutralization scheme ("accessible jellium"), which is a simplification of NECS. We demonstrate and compare the different neutralization schemes on several examples.
Organization Units (connected with the publication): Computational Material Design 
URL: https://aip.scitation.org/doi/10.1063/5.0021210
ISSN: 0021-9606
DOI: 10.1063/5.0021210
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