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Electronic structure calculations in electrolyte solutions: Methods for neutralization of extended charged interfaces

Electronic structure calculations in electrolyte solutions: Methods for neutralization of extended charged interfaces
Electronic structure calculations in electrolyte solutions: Methods for neutralization of extended charged interfaces

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.

0021-9606
Bhandari, Arihant
f2f12a89-273f-4c5e-a52e-e21835aaacfc
Anton, Lucian
da3a4e52-cdd8-45c2-97c0-174cfb6cbc45
Dziedzic, Jacek
8e2fdb55-dade-4ae4-bf1f-a148a89e4383
Peng, Chao
20f4467b-1786-4e11-97f2-2ab5885bcd7a
Kramer, Denis
1faae37a-fab7-4edd-99ee-ae4c30d3cde4
Skylaris, Chris Kriton
8f593d13-3ace-4558-ba08-04e48211af61
Bhandari, Arihant
f2f12a89-273f-4c5e-a52e-e21835aaacfc
Anton, Lucian
da3a4e52-cdd8-45c2-97c0-174cfb6cbc45
Dziedzic, Jacek
8e2fdb55-dade-4ae4-bf1f-a148a89e4383
Peng, Chao
20f4467b-1786-4e11-97f2-2ab5885bcd7a
Kramer, Denis
1faae37a-fab7-4edd-99ee-ae4c30d3cde4
Skylaris, Chris Kriton
8f593d13-3ace-4558-ba08-04e48211af61

Bhandari, Arihant, Anton, Lucian, Dziedzic, Jacek, Peng, Chao, Kramer, Denis and Skylaris, Chris Kriton (2020) Electronic structure calculations in electrolyte solutions: Methods for neutralization of extended charged interfaces. Journal of Chemical Physics, 153 (12), [124101]. (doi:10.1063/5.0021210).

Record type: Article

Abstract

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.

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Neutralization_paper - Accepted Manuscript
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Accepted/In Press date: 9 September 2020
e-pub ahead of print date: 22 September 2020

Identifiers

Local EPrints ID: 444834
URI: http://eprints.soton.ac.uk/id/eprint/444834
ISSN: 0021-9606
PURE UUID: 3817c412-203d-421e-92e8-1eba1a1dcb37
ORCID for Jacek Dziedzic: ORCID iD orcid.org/0000-0003-4786-372X
ORCID for Chris Kriton Skylaris: ORCID iD orcid.org/0000-0003-0258-3433

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Date deposited: 06 Nov 2020 17:30
Last modified: 26 Nov 2021 02:55

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Contributors

Author: Arihant Bhandari
Author: Lucian Anton
Author: Jacek Dziedzic ORCID iD
Author: Chao Peng
Author: Denis Kramer

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