Embedded Files
Estimating Ionic conductivity of Ionic Liquid: Nernst-Einstein and Einstein Formalism
Ionic conductivity plays an important role in the application of ionic liquids as electrolytes in next-generation batteries and electrochemical processes. It is often estimated using the Nernst–Einstein formalism in molecular simulation-based studies. The Nernst–Einstein formalism is useful for dilute systems where ions do not interact with each other, restricting its applicability to dilute solutions. However, this approximation fails in concentrated solutions where ion interactions become significant, which is usually encountered for pure ionic liquids. These ion-ion correlations can dramatically affect ionic conductivity predictions compared to those computed under the Nernst–Einstein formalism. This study highlights the challenges associated with calculating ionic conductivity using Einstein formalism and subsequently provides a workflow for such calculations. It has been found that a minimum trajectory length of 60 ns is required to achieve converged results for Einstein ionic conductivity. Guidance is also given to reduce the computational resource requirements for Einstein conductivity determination. This simplification will enable researchers to estimate Einstein conductivity in ionic liquids more efficiently. | See Journal of Ionic Liquids 2024, 4, 1, 100089.
Polarization and Charge Transfer Effects on Thermophysical Properties Predictions in Binary Ionic Liquid Mixtures
Imidazolium-based ionic liquids (ILs) offer various advantages, such as low volatility, non-flammability, exceptional thermal and chemical stability, and a wide electrochemical potential window, which makes them promising candidates for various applications, including electrolytic materials in electrochemical devices. While a large number of molecular simulation studies are available for predicting the ionic conductivity of pure ILs, little attention has been given to estimating ionic conductivity in ionic liquid-ionic liquid mixtures, especially considering that there is a possibility of observing non-ideal behavior due to differing polarizability of anions. Force fields based on fixed charge models may not be adequate to accurately model ionic liquid-ionic liquid mixtures. We evaluate two methodologies for assigning partial charges for estimating ionic conductivity of ionic liquid-ionic liquid mixtures: (a) partial charges are fixed as a function of concentration, and (b) partial charges vary with concentration. The partial atomic charges derived from electronic structure methods such as density functional theory (DFT) accurately account for the bulk environment. The fixed charge model sometimes leads to a qualitatively incorrect trend in the ionic conductivity as a function of concentration, necessitating the incorporation of variable charge models, while the variable-charge models correctly capture the experimental trend in ionic conductivities as a function of concentration, underscoring the role of modeling polarization in such systems. | See J. Phys. Chem. B 2025, 129, 9, 2546–2559..
Wetting, Friction, and Other Interfacial Phenomena at 2D Material Surfaces
Interfacial properties, such as wettability and friction, play critical roles in nanofluidics and desalination. Understanding the interfacial properties of two-dimensional (2D) materials is crucial in these applications due to the close interaction between liquids and solid surfaces. The most important interfacial properties of a solid surface include the water contact angle, which quantifies the extent of interactions between the surface and water, and the water slip length, which determines how much faster water can flow on the surface beyond the predictions of continuum fluid mechanics. Our research seeks to elucidate the mechanism that governs the interfacial properties of diverse 2D materials, including graphene, hexagonal boron nitride (hBN), and transition metal dichalcogenides (e.g., MoS2). We investigated the capabilities of density functional theory and molecular dynamics simulations in analyzing the interfacial properties of 2D materials. We find that the presence of surface roughness, but not that of vacancy defects, leads to remarkable agreement with the experimentally observed water contact angle of 66° on freshly synthesized, uncontaminated hBN. Additionally, the inclusion of surface roughness accurately predicts the experimental water slip length of ∼1 nm on hBN.| See Langmuir 2022, 38, 30, 9210–9220.
Influence of Pore Geometry on Interfacial Properties in 2D Nanomaterials
Our results underscore the importance of considering realistic models of 2D nan0materials while modeling nanomaterial–water interfaces in molecular simulations. Moreover, Our DFT calculations reveal a spatially varying charge distribution on these nanomaterials with pores, which we then incorporate into molecular dynamic (MD) simulations to elucidate their influence on the 2D nanomaterials–water interface. Our results indicate that pore size significantly impacts the wetting behavior of MoS2, whereas its effect on hBN is minimal. In contrast, the pore shape affects the wetting properties of both nanomaterials. Furthermore, the pore shape and size strongly influence the water flow rate through these pores. Notably, hBN performs better than MoS2 in triangular pores, while MoS2 shows a higher water flow rate in hexagonal pores. | See ACS Appl. Nano Mater. 2025, 8, 1, 904–914.
Google Sites
Report abuse