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Item type:Publication, Access status: with files , Equilibrium shape and surface termination of supported magnetite nanoparticles(Nature Publishing Group, 2026-12-01); ; ; ; The equilibrium shape and surface termination of magnetite nanoparticles (NPs) are fundamental properties that determine the physical and chemical properties of the supercrystal structure of oleic acid-coated magnetite NPs. Here, we studied the equilibrium shape of magnetite (Fe3O4) NPs supported by Al2O3(0001) single-crystalline surfaces. We report the growth of epitaxial (111)-oriented NPs exhibiting a triangular shape with a height-to-diameter aspect ratio of 0.42 over a wide growth temperature range. We probed the surface termination of the NP facets by adsorbing formic acid as a prototypical molecule representing the adsorption behavior of oleic acid. We identified infrared absorption bands characteristic of dissociative adsorption on (111) facets with the iron tetrahedral (Fetet1) termination, as well as on mixed-terminated (100) side facets. Our experimental findings are supported by predictions of the NP shape using surface-free energy calculations from ab initio thermodynamics. The experimentally observed nanoparticle shape can only be rationalized by the presence of bulk-terminated {100} type facets. Such a fundamental understanding of the shape and surface terminations of oxide nanoparticles is crucial for tailoring the properties of hybrid hierarchical materials and drug carriers and for their development.Publicationtype: Journal Article60 13 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: with files , Effect of anion hydrophobicity on the oxidation of ferrocene-terminated monolayersSelf-assembled monolayers (SAMs) terminated with ferrocene ((Formula presented.)) moieties are a popular model system for electron transfer processes at solid-liquid interfaces. Numerous experimental studies have found a correlation between the hydrophobicity of anions in the electrolyte and the redox potential. In this computational study, the redox potential is calculated for various anion species and SAM configurations using classical molecular dynamics. Thermodynamic integration and the constrained charge method are used to determine the redox potential as the free energy change associated with electron transfers from the (Formula presented.) moieties to the electrodes. The results show the anticipated lower redox potentials for hydrophobic anions and allow the study of changes at the solid-liquid interface at the atomistic level.Publicationtype: Journal Article57 53 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: with files , Efficient treatment of long-range electrostatics in charge equilibration approaches(American Institute of Physics (AIP), 2025-05-07); ; ; ; A charge equilibration method based on real-space Gaussians as charge densities is presented. The implementation is part of the Electrode package available in the Large-scale Atomic/Molecular Massively Parallel Simulator and benefits from its efficient particle-mesh Ewald approach. A simple strategy required to switch from the previously used Slater-type orbital (STO) shielding to Gaussians is provided by fitting the Coulomb energy of two Gaussian charge distributions to the repulsion between two STOs. Their widths were optimized for O, Si, and Ti species, obtaining results consistent with previous studies using STOs in the case of SiO2 polymorphs. In the limit of sufficiently narrow Gaussians, it is shown that the implementation converges to electronegativity equalization method results for the case of Ti/TiOx interfaces. The method presented is implemented in a way that is potentially beneficial for the application of modern machine-learning force fields that include long-range electrostatic interactions.Publicationtype: Journal Article36 74 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: with files , Effect of the reference choice on the contribution of molecular dipoles to the local electric potentialThe profile of the electric potential at interfaces is often employed in discussions of classical molecular dynamics models. However, in contrast to the total potential, the contribution of molecular dipoles to the potential depends on the choice of an arbitrary reference point within molecules. We show both analytically and in a simulation how this choice affects the dipole contribution in the bulk. The analytic derivation pinpoints the origin of the changes in the dipole contribution. The simulation verifies the analytic expression and shows the exact influence of the chosen molecular reference. This work highlights the inherent issues of the dipole contribution to the electric potential.Publicationtype: Journal Article12 17 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: without files , Atomistic modeling of functionalized nanporous metals at electric potentialsPublicationtype: Doctoral Thesis88 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: with files , Water, not salt, causes most of the Seebeck effect of nonisothermal aqueous electrolytes(American Physical Society (APS), 2024-05-03); ; ; A temperature difference between two electrolyte-immersed electrodes often yields a voltage Δψ between them. This electrolyte Seebeck effect is usually explained by cations and anions flowing differently in thermal gradients. However, using molecular simulations, we found almost the same Δψ for cells filled with pure water as with aqueous alkali halides. Water layering and orientation near polarizable electrodes cause a large temperature-dependent potential drop χ there. The difference in χ of hot and cold electrodes captures most of the thermovoltage, Δψ≈χhot-χcold.Publicationtype: Journal Article11 83 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: with files , ELECTRODE: an electrochemistry package for atomistic simulations(American Institute of Physics (AIP), 2022-08-25); ; ; Constant potential methods (CPM) enable computationally efficient simulations of the solid-liquid interface at conducting electrodes in molecular dynamics (MD). They have been successfully used, for example, to realistically model the behavior of ionic liquids or water-in-salt electrolytes in supercapacitors and batteries. The CPM models conductive electrodes by updating charges of individual electrode atoms according to the applied electric potential and the (time-dependent) local electrolyte structure. Here we present a feature-rich CPM implementation, called ELECTRODE, for the Large-scale Atomic/Molecular Massively Parallel Simulator (LAMMPS), which includes a constrained charge method and a thermo-potentiostat. The ELECTRODE package also contains a finite-field approach, multiple corrections for non-periodic boundary conditions of the particle-particle particle-mesh solver, and a Thomas-Fermi model for using non-ideal metals as electrodes. We demonstrate the capabilities of this implementation for a parallel-plate electrical double-layer capacitor, for which we have investigated the charging times with the different implemented methods and found an interesting relationship between water and ionic dipole relaxations. To prove the validity of the one-dimensional correction for the long-range electrostatics, we estimated the vacuum capacitance of two co-axial carbon nanotubes and compared it to structureless cylinders, for which an analytical expression exists. In summary, the ELECTRODE package enables efficient electrochemical simulations using state-of-the-art methods, allowing one to simulate even heterogeneous electrodes. Moreover, it allows unveiling more rigorously how electrode curvature affects the capacitance with the one-dimensional correction.Publicationtype: Journal ArticleScopus© Citations 19 201 530 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: with files , Constant potential simulations on a meshMolecular dynamics simulations in a constant potential ensemble are an increasingly important tool to investigate charging mechanisms in next-generation energy storage devices. We present a highly efficient approach to compute electrostatic interactions in simulations employing a constant potential method (CPM) by introducing a particle-particle particle-mesh solver specifically designed for treating long-range interactions in a CPM. Moreover, we present evidence that a dipole correction term—commonly used in simulations with a slab-like geometry—must be used with caution if it is also to be used within a CPM. It is demonstrated that artifacts arising from the usage of the dipole correction term can be circumvented by enforcing a charge neutrality condition in the evaluation of the electrode charges at a given external potential.Publicationtype: Journal ArticleScopus© Citations 12 161 695