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Item type:Publication, Access status: with files , Simultaneous learning of static and dynamic charges(Royal Society of Chemistry (RSC), 2026-06-01); ; ; Long-range interactions and electric response are essential for accurate modeling of condensed-phase systems, but capturing them efficiently remains a challenge for atomistic machine learning. Traditionally, these two phenomena can be represented by static charges that underlie Coulomb interactions between atoms, and dynamic charges such as atomic polar tensors—aka Born effective charges—describing the response to an external electric field. We critically compare different approaches to learn both types of charges within a single model architecture, taking bulk water and water clusters as paradigmatic examples: (1) learning them independently; (2) coupling static and dynamic charges based on their physical relationship with a single global coupling constant to account for dielectric screening; (3) coupled learning with a local, environment-dependent screening factor. In the coupled case, correcting for dielectric screening is essential, yet the common assumption of homogeneous, isotropic screening breaks down in heterogeneous systems such as water clusters. A learned, environment-dependent screening restores high accuracy for the dynamic charges. However, the accuracy gain over independent dynamic predictions is negligible, while the computational cost increases compared to using separate models for static and dynamic charges. This suggests that, despite the formal connection between the two charge types, modeling them independently is the more practical choice for both condensed-phase and isolated cluster systems.Publicationtype: Journal Article109 46 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: without files , Static dielectric permittivity profiles and coarse-graining approaches for water in graphene slit pores(AIP Publishing, 2026-03-27); ; ; ; The dielectric response of nano-confined fluids is important for a wide range of technologies and biological systems, ranging from the fundamentals of energy storage to the stability of lipid membrane bilayers. Its calculation from molecular simulations has become a viable tool since the 2010s and is often employed to rationalize experimental observations. However, confusion has emerged on the underlying boundary conditions, and correspondingly, the concept of dielectric profiles is often misunderstood in the literature. Here, we re-derive the Green–Kubo relation for the linear dielectric response profile of fluids in planar confinement, while carefully considering the different underlying boundary conditions; if the latter are correctly accounted for, profiles from equilibrium simulations are perfectly in line with results using externally applied fields. We discuss possible pitfalls and address misunderstandings, regarding both the detailed calculation and the general concept of dielectric profiles, as well as procedures to coarse-grain the microscopic dielectric behavior in order to connect to experimental observables. Simulations consistently reveal that the dielectric response of water is bulk-like down to confining scales as small as ∼1 nm. However, the effective dielectric response of confined systems, which determines their capacitance, depends on the precise location of the dielectric interface. Using concepts from effective medium theory, we show that the long-range reduction of the effective dielectric response, reported in both experimental and theoretical studies, is in line with a dielectric response that reaches the bulk value at about 1 nm from the surface. The effective dielectric response can be interpreted in terms of the commonly employed concept of an interfacial capacitance. We find that the dielectric properties of simulated water are independent of the simulation details and the water model employed, thus revealing the universal properties of water polarization correlations.Publicationtype: Journal Article4 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: without files , Water at charged interfaces(2021-07-01)11 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: without files , Universal and nonuniversal aspects of electrostatics in aqueous nanoconfinement(2020-05-04); ; ; ; Dielectric water properties, which significantly change in confinement, determine electrostatic interactions and thereby influence all molecular forces and chemical reactions. We present comparative simulations of water between graphene sheets, decanol monolayers, and phospholipid and glycolipid bilayers. Generally, dielectric profiles strongly differ in perpendicular and parallel surface directions and for large surface separation decay to the bulk value 1-2 nm away from the surface. Polar surface groups enhance the local interfacial dielectric response and for phospholipid bilayers induce a giant parallel contribution. A mapping on a box model with asymptotically determined effective water layer widths demonstrates that the perpendicular effective dielectric constant for all systems decreases for confinement below a nanometer, while the parallel one stays rather constant. The confinement-dependent perpendicular effective dielectric constant for graphene is in agreement with experimental data only if the effective water layer width is suitably adjusted. The interactions between two charges at small separation depend on the product of parallel and perpendicular effective water dielectric components; for large separation the interactions depend on the confining medium. For metallic confining media the interactions at large separation decay exponentially with a decay length that depends on the ratio of the effective parallel and perpendicular water dielectric components.Publicationtype: Journal Article4 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: without files , Giant axial dielectric response in water-fille nanotubes an effective electrostatic ion-ion interactions from a tensorial dielectric moel(American Chemical Society (ACS), 2019-11-25); ; ; ; Molecular ynamics simulations in conjunction with effective meium theory are use to investigate ielectric effects in water-fille nanotubes. The resulting effective axial ielectric constant shows a ivergent increase for small nanotube raii that epens on the nanotube length, while the effective raial ielectric constant ecreases significantly for thin nanotubes. By solving Poisson's equation for an anisotropic ielectric meium in cylinrical geometry, we show that the axial ion-ion interaction epens for small separations primarily on the raial ielectric constant, not on the axial one. This means that electrostatic ion-ion interactions in thin water-fille nanotubes are on the linear ielectric level significantly enhance ue to water confinement effects at small separations, while at large separations the outsie meium ominates. If the outsie meium is metallic, then the ion-ion interaction ecays exponentially for large ion separation.Publicationtype: Journal Article10 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: without files , Comment on “Hydrophobic surface enhances electrostatic interaction in water”(American Physical Society (APS), 2019-07-24); ; ; ; Publicationtype: Journal Article5 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: without files , Influence of polar co-solutes and salt on the hydration of lipid membranes(Royal Society of Chemistry (RSC), 2019); ; ; The influence of the co-solutes TMAO, urea, and NaCl on the hydration repulsion between lipid membranes is investigated in a combined experimental/simulation approach. Pressure-hydration curves obtained via sorption experiments reveal that the repulsion significantly increases when the membranes are loaded with co-solutes, most strongly for TMAO. As a result, the co-solutes retain additional water molecules and therefore provide membranes with a fluid and more physiological environment. The experimental data are quantitatively reproduced in complementary solvent-explicit atomistic molecular dynamics simulations, which yield the chemical potential of water. Simulation analysis reveals that the additional repulsion arises from the osmotic pressure generated by the co-solutes, an effect which is maximal for TMAO, due to its unfavorable interactions with the lipid headgroup layer and its extraordinarily high osmotic coefficient.Publicationtype: Journal Article7 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: without files , Breakdown of linear dielectric theory for the interaction between hydrated Ions and graphene(American Chemical Society (ACS), 2018-10-12); ; ; ; Many vital processes taking place in electrolytes, such as nanoparticle self-assembly, water purification, and the operation of aqueous supercapacitors, rely on the precise many-body interactions between surfaces and ions in water. Here we study the interaction between a hydrated ion and a charge-neutral graphene layer using atomistic molecular dynamics simulations. For small separations, the ion–graphene repulsion is of nonelectrostatic nature, and for intermediate separations, van der Waals attraction becomes important. Contrary to prevailing theory, we show that nonlinear and tensorial dielectric effects become non-negligible close to surfaces, even for monovalent ions. This breakdown of standard isotropic linear dielectric theory has important consequences for the understanding and modeling of charged objects at surfaces.Publicationtype: Journal Article44