Widom insertion method in simulations with Ewald summation

Bakhshandeh, Amin; Levin, Yan

doi:10.1063/5.0085527

Cited by 11 publications

(17 citation statements)

References 61 publications

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“…The excess chemical potential μ ex inside the reservoir can be calculated using a separate simulation. This can be done using Widom insertion method in a canonical MC with a fixed concentration of acid and salt in a cubic simulation cell with periodic boundary conditions, or using a reverse GCMC strategy in which the value of μ ex in GCMC is adjusted until the target concentration inside the simulation cell is reached. , In order to accurately calculate the excess chemical potential for a specific concentration of acid and salt inside an infinite reservoir, it is important to use Ewald summation to treat all the electrostatic interactions between ions.…”

Section: Reactive Monte Carlo Simulationsmentioning

confidence: 99%

Theory of Charge Regulation of Colloidal Particles in Electrolyte Solutions

2022

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We present a theory that enables us to (i) calculate the effective surface charge of colloidal particles and (ii) efficiently obtain titration curves for different salt concentrations. The theory accounts for the shift of pH of solution due to the presence of 1:1 electrolyte. It also accounts self-consistently for the electrostatic potential produced by the deprotonated surface groups. To examine the accuracy of the theory, we have performed extensive reactive Monte Carlo simulations, which show excellent agreement between theory and simulations without any adjustable parameters.

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Section: Reactive Monte Carlo Simulationsmentioning

confidence: 99%

Theory of Charge Regulation of Colloidal Particles in Electrolyte Solutions

2022

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“…The excess chemical potential µ ex inside the reservoir can be calculated using a separate simulation. This can be done using Widom insertion method in a canonical MC with fixed concentration of acid and salt in a cubic simulation cell with periodic boundary conditions, or using a reverse GCMC strategy in which the value of µ ex in GCMC is adjusted until the target concentration inside the simulation cell is reached 62,63 . In order to accurately calculate the excess chemical potential for a specific concentration of acid and salt inside an infinite reservoir it is important to use Ewald summation to treat all the electrostatic interactions between ions.…”

Section: Reactive Monte Carlo Simulationsmentioning

confidence: 99%

Theory of Charge Regulation of Colloidal Particles in Electrolyte Solutions

Bakhshandeh¹,

Frydel²,

Levin³

2022

Preprint

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We present a theory that enables us to calculate the effective surface charge of colloidal particles and to efficiently obtain titration curves for different salt concentrations. The theory accounts for the shift of pH of solution due to the presence of 1:1 electrolyte. It also accounts self-consistently for the electrostatic potential produced by the deprotonated surface groups. To examine the accuracy of the theory we have performed extensive reactive Monte Carlo simulations, which show excellent agreement between theory and simulations without any adjustable parameters.

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“…If one is interested in studying closed systems, the rGCMCD approach is not very convenient since it calls for the specification of the chemical potential of all ions inside the reservoir in order to perform the GC moves. This requires a separate simulation of the reservoir, in which, the Widom insertion method is used to obtain the chemical potential of all the ions. − Furthermore, the calculation of the Donnan potential within the GC formalism makes such simulations slow. Recently, we have developed a new method for canonical titration simulations utilizing the surface Widom insertion algorithm that enables us to easily calculate equilibrium pH .…”

Section: Introductionmentioning

confidence: 99%

On the Validity of Constant pH Simulations

Bakhshandeh,

Levin

2024

J. Chem. Theory Comput.

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Constant pH (cpH) simulations are now a standard tool for investigating charge regulation in coarse-grained models of polyelectrolytes and colloidal systems. Originally developed for studying solutions with implicit ions, extending this method to systems with explicit ions or solvents presents several challenges. Ensuring proper charge neutrality within the simulation cell requires performing titration moves in sync with the insertion or deletion of ions, a crucial aspect often overlooked in the literature. Contrary to the prevailing views, cpH simulations are inherently grand-canonical, meaning that the controlled pH is that of the reservoir. The presence of the Donnan potential between the implicit reservoir and the simulation cell introduces significant differences between titration curves calculated for open and closed systems; the pH of an isolated (closed) system is different from the pH of the reservoir for the same protonation state of the polyelectrolyte. To underscore this point, in this paper, we will compare the titration curves calculated using the usual cpH algorithm with those from the exact canonical simulation algorithm. In the latter case, titration moves adhere to the correct detailed balance condition, and pH is calculated using the recently introduced surface Widom insertion algorithm. Our findings reveal a very significant difference between the titration isotherms obtained using the standard cpH algorithm and the canonical titration algorithm, emphasizing the importance of using the correct simulation approach when studying charge regulation of polyelectrolytes, proteins, and colloidal particles.

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Widom insertion method in simulations with Ewald summation

Cited by 11 publications

References 61 publications

Theory of Charge Regulation of Colloidal Particles in Electrolyte Solutions

Theory of Charge Regulation of Colloidal Particles in Electrolyte Solutions

Theory of Charge Regulation of Colloidal Particles in Electrolyte Solutions

On the Validity of Constant pH Simulations

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