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Item type:Publication, Access status: without files , Interfacial ion hydration and electrostatics govern salt precipitation and crystal morphology(2025-12-28); ; ; Salt precipitation, a phenomenon central to processes such as soil salinization, water treatment, and energy storage, is dictated by nanoscale hydration and electrostatic interactions at crystal interfaces. Understanding how their interplay gives rise to salt-specific growth behaviors and morphologies remains a critical challenge. Combining large-scale molecular dynamics simulations with free energy calculations, we investigate the precipitation behavior of three common salts, namely, NaCl, KCl, and Na2SO4, on their respective crystal surfaces. While all crystals grow steadily under controlled supersaturation, their surface morphologies differ markedly. KCl grows in a nearly ideal layer-by-layer mode, whereas NaCl and Na2SO4 develop increasingly rough, defect-rich surfaces. This roughening is accompanied by an early-stage charge imbalance at the crystal surface, characterized by preferential cation adsorption. The resulting local electrostatic environment modifies the structuring and dynamics of interfacial water, which in turn facilitates the premature growth of subsequent layers. We further find that ion adsorption is strongly defect-dependent: kinks provide stabilizing environments, whereas steps are energetically unfavorable due to their distinct hydration. Our study offers molecular-level insight into the coupled roles of ion-specific adsorption and interfacial hydration in shaping crystal morphology for different salts.Publicationtype: Journal Article61 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: with files , A lattice Boltzmann approach for modeling coupled evaporation/precipitation processes in porous media(ESS Open Archive, 2025-11-06); ; We present a novel numerical approach for simulating coupled evaporation and salt precipitation processes in porous media using the lattice Boltzmann method. Our model combines a Shan-Chen multiphase flow framework with a volume-based discretization method for diffusing salt species, where the coupling mechanism operates through solvation energy differences. The framework incorporates a precipitation model based on first-order reaction kinetics, enabling the transformation of fluid cells into solid crystal cells upon reaching threshold concentrations. We verify our model against analytical solutions for crystal growth and evaporation rates, demonstrating excellent agreement. The model is then applied to investigate the influence of wetting properties on evaporation and salt precipitation in porous media. Our simulations reveal that the wettability of both the porous medium and the precipitated salt crystals has a significant impact on precipitation patterns and pore clogging. Notably, increased salt crystal wettability promotes more effective pore blocking, substantially reducing permeability and evaporation rates. We find that the slowest evaporation occurs when salt crystals have high wettability, while the porous medium exhibits lower wettability because this configuration maximizes pore clogging. This work presents a novel framework to gain insight into the intricate interplay between fluid dynamics, wetting properties, and salt precipitation in porous media, with implications for understanding soil salinization, building material degradation, and the formation of geological salt crusts.Publicationtype: Preprint33 24 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: without files , Intermittent molecular motion and first passage statistics for the NMR relaxation of confined waterThe structure and dynamics of fluids confined in nanoporous media differ from those in bulk, which can be probed using NMR relaxation measurements. We here show, using atomistic molecular dynamics simulations of water in a slit nanopore, that the behavior of the NMR relaxation rate, R_{1}, with varying surface interaction and confinement strength can be estimated from the exchange statistics of fluid molecules between the adsorbed surface layer and the bulk region. In detail, we test the applicability of intermittent molecular water dynamics, a theoretical framework that relates NMR relaxation to the statistics of molecular exchange between these two states. We confront this framework with the direct evaluation of dipolar NMR relaxation rates from atomistic molecular dynamics simulations of water confined in a slit nanopore, allowing to assess its accuracy across varying surface interactions. We employ first return passage time calculations to quantify the molecular exchange statistics, thereby linking microscopic parameters of the confined fluid-such as adsorption time, pore size, and diffusion coefficient-to the NMR relaxation rate. Our results show that the theoretical framework proposed by Levitz et al. captures the qualitative trends of NMR relaxation rates observed in our molecular simulations. This approach allows to predict, interpret, and analyze the molecular relaxation of fluids at interfaces using merely concepts of statistical mechanics that can be generalized to closed and open geometries and thus yields direct insights into the experimental study of NMR relaxation with varying surface chemistry or confinement strength.Publicationtype: Journal Article29 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: without files , Disentanglement of Surface and Confinement Effects for Diene Metathesis in Mesoporous ConfinementWe study the effects of a planar interface and confinement on a generic catalytically activated ring-closing polymerization reaction near an unstructured catalyst. For this, we employ a coarse-grained polymer model using grand-canonical molecular dynamics simulations with a Monte Carlo reaction scheme. Inspired by recent experiments in the group of M. Buchmeiser that demonstrated an increase in ring-closing selectivity under confinement, we show that both the interface effects, i.e., placing the catalyst near a planar wall, and the confinement effects, i.e., locating the catalyst within a pore, lead to an increase of selectivity. We furthermore demonstrate that curvature effects for cylindrical mesopores (2 nm < d < 12.3 nm) influence the distribution of the chain ends, leading to a further increase in selectivity. This leads us to speculate that specially corrugated surfaces might also help to enhance catalytically activated polymerization processes.Publicationtype: Journal Article10 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: without files , Solvent Effects on Structure and Screening in Confined Electrolytes(American Physical Society (APS), 2023-09-11); 12 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: without files , Renormalized charge and dielectric effects in colloidal interactions: a numerical solution of the nonlinear Poisson–Boltzmann equation for unknown boundary conditions(Springer, 2023-09-11); ; ; Abstract: The Derjaguin–Landau–Verwey–Overbeek (DLVO) theory, introduced more than 70 years ago, is a hallmark of colloidal particle modeling. For highly charged particles in the dilute regime, it is often supplemented by Alexander’s prescription (Alexander et al. in J Chem Phys 80:5776, 1984) for using a renormalized charge. Here, we solve the problem of the interaction between two charged colloids at finite ionic strength, including dielectric mismatch effects, using an efficient numerical scheme to solve the nonlinear Poisson–Boltzmann (NPB) equation with unknown boundary conditions. Our results perfectly match the analytical predictions for the renormalized charge by Trizac and coworkers (Aubouy et al. in J Phys A 36:5835, 2003). Moreover, they allow us to reinterpret previous molecular dynamics (MD) simulation results by Kreer et al. (Phys Rev E 74:021401, 2006), rendering them now in agreement with the expected behavior. We furthermore find that the influence of polarization becomes important only when the Debye layers overlap significantly. Graphical Abstract: [Figure not available: see fulltext.].Publicationtype: Journal Article50 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: without files , A screening of results on the decay length in concentrated electrolytes(Royal Society of Chemistry (RSC), 2023-08-21); 12 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: without files , Assessing the validity of NMR relaxation rates obtained from coarse-grained simulations of PEG-water mixtures(American Chemical Society (ACS), 2023-06-16); ; ; ; NMR relaxometry is a powerful and well-established experimental approach for characterizing dynamic processes in soft matter systems. All-atom (AA) resolved simulations are typically employed to gain further microscopic insights while reproducing the relaxation rates R1. However, such approaches are limited to time and length scales that prevent to model systems such as long polymer chains or hydrogels. Coarse graining (CG) can overcome this barrier at the cost of losing atomistic details that impede the calculation of NMR relaxation rates. Here, we address this issue by performing a systematic characterization of dipolar relaxation rates R1 on a PEG-H2O mixture at two different levels of details: AA and CG. Remarkably, we show that NMR relaxation rates R1 obtained at the CG level obey the same trends when compared to AA calculations but with a systematic offset. This offset is due to, on the one hand, the lack of an intramonomer component and, on the other hand, the inexact positioning of the spin carriers. We show that the offset can be corrected for quantitatively by reconstructing a posteriori the atomistic details for the CG trajectories.Publicationtype: Journal Article17 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: without files , NMR investigation of water in salt crusts: insights from experiments and molecular simulations(American Chemical Society (ACS), 2023-05-19); ; ; ; The evaporation of water from bare soil is often accompanied by the formation of a layer of crystallized salt, a process that must be understood in order to address the issue of soil salinization. Here, we use nuclear magnetic relaxation dispersion measurements to better understand the dynamic properties of water within two types of salt crusts: sodium chloride (NaCl) and sodium sulfate (Na2SO4). Our experimental results display a stronger dispersion of the relaxation time T1 with frequency for the case of sodium sulfate as compared to sodium chloride salt crusts. To gain insight into these results, we perform molecular dynamics simulations of salt solutions confined within slit nanopores made of either NaCl or Na2SO4. We find a strong dependence of the value of the relaxation time T1 on pore size and salt concentration. Our simulations reveal the complex interplay between the adsorption of ions at the solid surface, the structure of water near the interface, and the dispersion of T1 at low frequency, which we attribute to adsorption-desorption events.Publicationtype: Journal Article9 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: without files , Transport of thin water films: From thermally activated random walks to hydrodynamics(American Institute of Physics (AIP), 2022-09-14); ; Under ambient atmospheric conditions, a thin film of water wets many solid surfaces, including insulators, ice, and salt. The film thickness as well as its transport behavior sensitively depend on the surrounding humidity. Understanding this intricate interplay is of the highest relevance for water transport through porous media, particularly in the context of soil salinization induced by evaporation. Here, we use molecular simulations to evaluate the transport properties of thin water films on prototypical salt and soil interfaces, namely NaCl and silica solid surfaces. Our results show two distinct regimes for water transport: at low water coverage, the film permeance scales linearly with the adsorbed amount, in agreement with the activated random walk model. For thicker water films, the permeance scales as the adsorbed amount to the power of 3, in line with the Stokes equation. By comparing results obtained for silica and NaCl surfaces, we find that, at low water coverage, water permeance at the silica surface is considerably lower than at the NaCl surface, which we attribute to difference in hydrogen bonding. We also investigate the effect of atomic surface defects on the transport properties. Finally, in the context of water transport through the porous material, we determine the humidity-dependent crossover between a vapor-dominated and a thin film-dominated transport regimes depending on the pore size.Publicationtype: Journal Article7