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arXiv · 2610.23291

Electrochemical Molecular Dynamics within the Finite-Field Framework

Krystof Brezina·Ludwig Ahrens-Iwers·Mariana Rossi
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Abstract

Electrochemical processes at charged interfaces lie at the heart of modern technologies and their continued improvement depends on insights into the relevant atomistic processes. However, the necessary tools to impose constant-voltage conditions in molecular dynamics (MD) simulations typically directly target the electrode charge, making their extension to methods that go beyond an empirical description of metals more cumbersome. In this work, we propose an MD protocol to realize a thermodynamic ensemble in which voltage control is attained, but which is formulated purely within the framework of finite-field simulations in 3D periodic boundary conditions. We show a derivation and implementation of such a control device, which we coin an electrostat, in the ELECTRODE package within LAMMPS. Our simulations systematically benchmark the derived theory against other established approaches, for example, showing its equivalence to a potentiostat, and quantify the importance of properly accounting for ensemble fluctuations. We find that for systems of several thousands of atoms, one obtains the same equilibrium properties with the electrostat as with a simpler constant-field simulation. The difference between the two methods only manifests itself at smaller length scales, thereby establishing practical limits for the inclusion of voltage fluctuations in atomistic simulations of electrochemical systems. The strength of this framework also lies in its simplicity of extension to first-principles ab initio and reactive machine-learning potentials.

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Krystof Brezina, Ludwig Ahrens-Iwers, Mariana Rossi. 2026-10-16. Electrochemical Molecular Dynamics within the Finite-Field Framework. https://arxiv.org/abs/2610.23291

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