The Experts below are selected from a list of 360 Experts worldwide ranked by ideXlab platform
Benjamin Rotenberg - One of the best experts on this subject based on the ideXlab platform.
-
charge fluctuations from molecular simulations in the Constant Potential ensemble
Physical Chemistry Chemical Physics, 2020Co-Authors: Laura Scalfi, David T Limmer, Alessandro Coretti, Sara Bonella, Paul A Madden, Mathieu Salanne, Benjamin RotenbergAbstract:We revisit the statistical mechanics of charge fluctuations in capacitors. In Constant-Potential classical molecular simulations, the atomic charges of electrode atoms are treated as additional degrees of freedom which evolve in time so as to satisfy the constraint of fixed electrostatic Potential for each configuration of the electrolyte. The present work clarifies the role of the overall electroneutrality constraint, as well as the link between the averages computed within the Born–Oppenheimer approximation and that of the full Constant-Potential ensemble. This allows us in particular to derive a complete fluctuation–dissipation relation for the differential capacitance, that includes a contribution from the charge fluctuations (around the charges satisfying the Constant-Potential and electroneutrality constraints) also present in the absence of an electrolyte. We provide a simple expression for this contribution from the elements of the inverse of the matrix defining the quadratic form of the fluctuating charges in the energy. We then illustrate numerically the validity of our results, and recover the expected continuum result for an empty capacitor with structureless electrodes at large inter-electrode distances. By considering a variety of liquids between graphite electrodes, we confirm that this contribution to the total differential capacitance is small compared to that induced by the thermal fluctuations of the electrolyte.
-
simulating electrochemical systems by combining the finite field method with a Constant Potential electrode
Physical Review Letters, 2019Co-Authors: Thomas Dufils, Benjamin Rotenberg, Guillaume Jeanmairet, Michiel Sprik, Mathieu SalanneAbstract:A better understanding of interfacial mechanisms is needed to improve the performances of elec-trochemical devices. Yet, simulating an electrode surface at fixed electrolyte composition remains a challenge. Here we apply a finite electric field to a single electrode held at Constant Potential and in contact with an aqueous ionic solution, using classical molecular dynamics. The polarization yields two electrochemical interfaces on opposite sides of the same metal slab. While the net charge on one electrode surface is the opposite of the net charge on the other, maintaining overall charge neutrality of the metal. The electrode surface charges fluctuations are compensated by the adsorption of ions from the electrolyte, forming a pair of electric double layers with aligned dipoles. This opens the way towards the efficient simulation of electrochemical interfaces using any flavor of molecular dynamics, from classical to first principles-based methods.
Hirofumi Sato - One of the best experts on this subject based on the ideXlab platform.
-
a chemical Potential equalization approach to Constant Potential polarizable electrodes for electrochemical cell simulations
Journal of Chemical Physics, 2019Co-Authors: Hiroshi Nakano, Hirofumi SatoAbstract:Atomistic modeling of electrochemical systems is one of the most challenging topics in the field of molecular simulations. We derive the equations for modeling Constant Potential polarizable electrodes in electrochemical-cell simulations based on the chemical Potential equalization principle. They reduce to those derived by Siepmann and Sprik [J. Chem. Phys. 102, 511 (1995)], later arranged by Reed, Lanning, and Madden [J. Chem. Phys. 126, 084704 (2007)] under some assumptions. The present approach clarifies the physical meaning of the total energy of a system that includes classical polarizable electrodes, which is important in order to analyze the energetics of chemical phenomena at electrode-electrolyte interfaces. The effects of the Hubbard U parameter of an electrode atom are discussed in connection with the perfect conductor limit for a metal electrode.
-
Constant Potential molecular dynamics simulations on an electrode electrolyte system calculation of static quantities and comparison of two polarizable metal electrode models
Chemical Physics Letters, 2017Co-Authors: Yusuke Matsumi, Hiroshi Nakano, Hirofumi SatoAbstract:Abstract We investigated a Pt electrode-water molecules system by Constant Potential molecular dynamics simulations using two different models for electronically polarizable metal electrodes. Static quantities were calculated such as the number density profiles, electrostatic Potential profiles, and the Potential of mean force profiles for the approach of a Na + to an electrode. The two models were compared to find out they give results in good agreement with each other. The electrostatic Potential acting on the Na + was also evaluated and decomposed to get insight into the importance of the interactions between a redox species and polarizable metal electrodes.
Brian B Laird - One of the best experts on this subject based on the ideXlab platform.
-
evaluation of the Constant Potential method in simulating electric double layer capacitors
Journal of Chemical Physics, 2014Co-Authors: Zhenxing Wang, Yang Yang, David L Olmsted, Mark Asta, Brian B LairdAbstract:A major challenge in the molecular simulation of electric double layer capacitors (EDLCs) is the choice of an appropriate model for the electrode. Typically, in such simulations the electrode surface is modeled using a uniform fixed charge on each of the electrode atoms, which ignores the electrode response to local charge fluctuations in the electrolyte solution. In this work, we evaluate and compare this Fixed Charge Method (FCM) with the more realistic Constant Potential Method (CPM), [S. K. Reed et al., J. Chem. Phys. 126, 084704 (2007)], in which the electrode charges fluctuate in order to maintain Constant electric Potential in each electrode. For this comparison, we utilize a simplified LiClO4-acetonitrile/graphite EDLC. At low Potential difference (ΔΨ ⩽ 2 V), the two methods yield essentially identical results for ion and solvent density profiles; however, significant differences appear at higher ΔΨ. At ΔΨ ⩾ 4 V, the CPM ion density profiles show significant enhancement (over FCM) of “inner-sphere...
-
evaluation of Constant Potential method in simulating electric double layer capacitors
arXiv: Computational Physics, 2014Co-Authors: Zhenxing Wang, Yang Yang, David L Olmsted, Mark Asta, Brian B LairdAbstract:A major challenge in the molecular simulation of electric double layer capacitors (EDLCs) is the choice of an appropriate model for the electrode. Typically, in such simulations the electrode surface is modeled using a uniform fixed charge on each of the electrode atoms, which ignores the electrode response to local charge fluctuations induced by charge fluctuations in the electrolyte. In this work, we evaluate and compare this Fixed Charge Method (FCM) with the more realistic Constant Potential Method (CPM), [Reed, et al., J. Chem. Phys., 126, 084704 (2007)], in which the electrode charges fluctuate in order to maintain Constant electric Potential in each electrode. For this comparison, we utilize a simplified LiClO$_4$-acetonitrile/graphite EDLC. At low Potential difference ($\Delta\Psi\le 2V$), the two methods yield essentially identical results for ion and solvent density profiles; however, significant differences appear at higher $\Delta\Psi$. At $\Delta\Psi\ge 4V$, the CPM ion density profiles show significant enhancement (over FCM) of "partially electrode solvated" Li$^+$ ions very close to the electrode surface. The ability of the CPM electrode to respond to local charge fluctuations in the electrolyte is seen to significantly lower the energy (and barrier) for the approach of Li$^+$ ions to the electrode surface.
Hannes Jonsson - One of the best experts on this subject based on the ideXlab platform.
-
Assessment of Constant-Potential Implicit Solvation Calculations of Electrochemical Energy Barriers for H2 Evolution on Pt
Journal of Physical Chemistry C, 2019Co-Authors: Maxime Van Den Bossche, Christoph Rose-petruck, Egill Skulason, Hannes JonssonAbstract:Theoretical estimation of the activation energy of electrochemical reactions is of critical importance but remains challenging. In this work, we address the usage of an implicit solvation model for...
-
assessment of Constant Potential implicit solvation calculations of electrochemical energy barriers for h evolution on pt
The Journal of Physical Chemistry, 2019Co-Authors: Maxime Van Den Bossche, Egill Skulason, Christoph Rosepetruck, Hannes JonssonAbstract:Theoretical estimation of the activation energy of electrochemical reactions is of critical importance but remains challenging. In this work, we address the usage of an implicit solvation model for describing hydrogen evolution reaction steps on Pt(111) and Pt(110) and compare with the “extrapolation” approach as well as single-crystal measurements. We find that both methods yield qualitatively similar results, which are in fair agreement with the experimental data. Care should be taken, however, in addressing spurious electrostatic interactions between periodically repeated slabs in the VASPsol implementation. Considering the lower computational cost and higher flexibility of the implicit solvation approach, we expect this method to become a valuable tool in electrocatalysis.
-
Assessment of Constant-Potential Implicit Solvation Calculations of Electrochemical Energy Barriers for H2 evolution on Pt
2018Co-Authors: Maxime Van Den Bossche, Egill Skúlason, Christoph Rose-petruck, Hannes JonssonAbstract:Theoretical estimation of the activation energy of electrochemical reactions is of critical importance but remains challenging. In this work, we address the usage of an implicit solvation model for describing hydrogen evolution reaction steps on Pt(111) and Pt(110), and compare with the `extrapolation' approach as well as single-crystal measurements. We find that both methods yield qualitatively similar results, which are in fair agreement with the experimental data. Care should be taken, however, in addressing spurious electrostatic interactions between periodically repeated slabs in the VASPsol implementation. Considering the lower computational cost and higher flexibility of the implicit solvation approach, we expect this method to become a valuable tool in electrocatalysis.<br>
Mathieu Salanne - One of the best experts on this subject based on the ideXlab platform.
-
charge fluctuations from molecular simulations in the Constant Potential ensemble
Physical Chemistry Chemical Physics, 2020Co-Authors: Laura Scalfi, David T Limmer, Alessandro Coretti, Sara Bonella, Paul A Madden, Mathieu Salanne, Benjamin RotenbergAbstract:We revisit the statistical mechanics of charge fluctuations in capacitors. In Constant-Potential classical molecular simulations, the atomic charges of electrode atoms are treated as additional degrees of freedom which evolve in time so as to satisfy the constraint of fixed electrostatic Potential for each configuration of the electrolyte. The present work clarifies the role of the overall electroneutrality constraint, as well as the link between the averages computed within the Born–Oppenheimer approximation and that of the full Constant-Potential ensemble. This allows us in particular to derive a complete fluctuation–dissipation relation for the differential capacitance, that includes a contribution from the charge fluctuations (around the charges satisfying the Constant-Potential and electroneutrality constraints) also present in the absence of an electrolyte. We provide a simple expression for this contribution from the elements of the inverse of the matrix defining the quadratic form of the fluctuating charges in the energy. We then illustrate numerically the validity of our results, and recover the expected continuum result for an empty capacitor with structureless electrodes at large inter-electrode distances. By considering a variety of liquids between graphite electrodes, we confirm that this contribution to the total differential capacitance is small compared to that induced by the thermal fluctuations of the electrolyte.
-
simulating electrochemical systems by combining the finite field method with a Constant Potential electrode
Physical Review Letters, 2019Co-Authors: Thomas Dufils, Benjamin Rotenberg, Guillaume Jeanmairet, Michiel Sprik, Mathieu SalanneAbstract:A better understanding of interfacial mechanisms is needed to improve the performances of elec-trochemical devices. Yet, simulating an electrode surface at fixed electrolyte composition remains a challenge. Here we apply a finite electric field to a single electrode held at Constant Potential and in contact with an aqueous ionic solution, using classical molecular dynamics. The polarization yields two electrochemical interfaces on opposite sides of the same metal slab. While the net charge on one electrode surface is the opposite of the net charge on the other, maintaining overall charge neutrality of the metal. The electrode surface charges fluctuations are compensated by the adsorption of ions from the electrolyte, forming a pair of electric double layers with aligned dipoles. This opens the way towards the efficient simulation of electrochemical interfaces using any flavor of molecular dynamics, from classical to first principles-based methods.