The thermophysical properties of aqueous electrolyte solutions are of interest for applications such as water electrolyzers and fuel cells. Molecular dynamics (MD) and continuous fractional component Monte Carlo (CFCMC) simulations are used to calculate densities, transport properties (i.e., self-diffusivities and dynamic viscosities), and solubilities of H2 and O2 in aqueous sodium and potassium hydroxide (NaOH and KOH) solutions for a wide electrolyte concentration range (0-8 mol/kg). Simulations are carried out for a temperature and pressure range of 298-353 K and 1-100 bar, respectively. The TIP4P/2005 water model is used in combination with a newly parametrized OH- force field for NaOH and KOH. The computed dynamic viscosities at 298 K for NaOH and KOH solutions are within 5% from the reported experimental data up to an electrolyte concentration of 6 mol/kg. For most of the thermodynamic conditions (especially at high concentrations, pressures, and temperatures) experimental data are largely lacking. We present an extensive collection of new data and engineering equations for H2 and O2 self-diffusivities and solubilities in NaOH and KOH solutions, which can be used for process design and optimization of efficient alkaline electrolyzers and fuel cells.

The role of ionic liquid in asphaltene dissolution is studied using experimental characterization techniques, such as optical microscopic imaging analysis, 13C nuclear magnetic resonance (NMR), and Fourier transform infrared (FTIR) spectroscopy, along with molecular insights achieved using classical molecular dynamics (MD) simulations. The dissolution behavior of the asphaltenes in 1-butyl-3-methylimidazolium hexafluorophosphate ([BMIM][PF6]) ionic liquid along with organic solvents, i.e., toluene and hexane, is investigated using optical images. The behavior of asphaltene aggregates in the solvent plus ionic liquid mixture is probed using FTIR and 13C NMR spectroscopic techniques. The structural and dynamical properties of the asphaltene aggregates mainly end-to-end distance, the diffusion coefficient of the asphaltene molecules, and the trajectory density contour of the asphaltene in the solvent plus ionic liquid mixture are probed using MD simulations. It is concluded from our combined experimental-MD study that the ionic liquid plays a key role in asphaltene separation from organic solvents under study.

Doxorubicin is cytotoxic anthracycline antibiotic drug used in cancer treatment. The drug's efficacy in various kinds of cancer made its usage dominant for treating cancers. In this study, we determined the solubility of the doxorubicin in three different polymers, i.e., poly (N-isopropyl acrylamide), polyethylene glycol, and polyvinyl pyrrolidone, to increase the doxorubicin's drug efficacy on the targeted tumor site. We investigated the doxorubicin-polymer interactions with carbon-nanotube in the aqueous environment for the targeted delivery application using classical molecular dynamics simulations. An in-depth atomistic insight into polymer interaction with the drug/carbon-nanotube/water is obtained within the study. We have critically analyzed various properties such as interaction energy, hydrogen bonds between polymer-drug and polymer-water, the diffusion coefficient of the drug, end-to-end distance, radius of gyration of the polymer chains, and finally, drug density contours for different drug to polymer ratios. Our results explain the selection of effective monomer chain length of polymer and the suitability of the polymer carrier with doxorubicin.

Controlling the detrimental effect of hydrogen on the mechanical behaviour of advanced high strength steels is decisive for their application. Precipitates in steels can be useful in irreversibly trapping the hydrogen atoms, thereby preventing their diffusion to critical regions in the microstructure where they can be most detrimental. In this work, the capability of precipitates of transition metals in limiting the amount of diffusible hydrogen has been examined. A combined ab initio–experimental approach was used to study the hydrogen sorption in two DP800 steel grades with different concentrations of titanium and vanadium using cyclic voltammetry. Under the same charging conditions, diffusible hydrogen concentration was found to be higher in the vanadium grade as compared to the titanium grade. Scanning electron microscope characterisation revealed a more compact layer of oxide on the vanadium grade which contributed to more hydrogen absorption on the surface. Density Functional Theory calculations were performed to determine the trapping strength of precipitates of titanium and vanadium. C vacancy in titanium carbide was found to be the strongest hydrogen trap, but the C vacancy formation energy was much lower in vanadium carbide. At finite temperatures, however, both precipitates are experimentally known to be off-stoichiometric. Our DFT-based finding of the titanium grade being irreversible hydrogen trap is thus in agreement with the experimental results.

The aggregation behavior of asphaltene in the toluene-hexane mixture is systematically investigated using experimental techniques such as optical microscopy and Fourier-transform infrared spectroscopy (FTIR) combined with molecular dynamics (MD) simulations. The optical images of various asphaltene concentrations are processed to determine the size of asphaltene aggregates. FTIR is performed within our work in order to understand the formation of aggregates and its interaction with the solvent mixture. MD simulations are employed to achieve atomistic insights into the aggregation behavior of asphaltene. The end-to-end distance of the asphaltene molecule is calculated for various asphaltene concentrations in the toluene-hexane mixture. The dynamical properties of the asphaltene aggregates such as the diffusion coefficient and shear viscosity are calculated. Further, an in-depth analysis of the density contours is performed to probe the clusterization of asphaltene. Thus obtained structural and dynamical properties of the asphaltene aggregates in the toluene-hexane mixture are compared with our experimental findings. Our results thereby highlight the importance of the combined experimental and theoretical study to achieve deeper and better insights into the aggregation behavior of asphaltene in toluene-hexane mixture.

Two-dimensional (2D) boron-based materials are receiving much attention as H2 storage media due to the low atomic mass of boron and the stability of decorating alkali metals on the surface, which enhance interactions with H2. This work investigates the suitability of Li, Na, and K decorations on 2D honeycomb borophene oxide (B2O) for H2 storage, using dispersion corrected density functional theory (DFT-D2). A high theoretical gravimetric density of 8.3 wt % H2 is achieved for the Li-decorated B2O structure. At saturation, each Li binds to two H2 with an average binding energy of -0.24 eV/H2. Born-Oppenheimer molecular dynamics simulations at temperatures of 100, 300, and 500 K demonstrate the stability of the Li-decorated structure and the H2 desorption behavior at different temperatures. Our findings indicate that Li-decorated 2D B2O is a promising material for reversible H2 storage and recommend experimental investigation of 2D B2O as a potential H2 storage medium.

Tailoring nanostructures is nowadays a common approach for enhancing the performance of thermoelectric Heusler compounds by decreasing the thermal conductivity without significantly affecting the electrical conductivity. However, the most widely reported method for obtaining nanostructured thermoelectrics, an approach based on crushing as-cast alloy ingots followed by sintering of the debris, only gives limited control of the final nanostructure due to residual elemental segregation after casting. Here, a novel approach for fabricating nanostructured Heusler compounds is presented, which is based on crystallizing an amorphous precursor of NbCo_1.1Sn composition. This method yields two distinct nanostructures, namely one comprising only half-Heusler grains and another one comprising half-Heusler grains and full-Heusler nano-precipitates. The latter sample exhibits enhanced negative Seebeck coefficients as compared to the former over a wide temperature range. Using advanced characterization techniques, such as high-resolution transmission electron microscopy and atom probe tomography, in conjunction with ab initio density functional theory, detailed insights into the nanostructure and electrical properties of the specimens are provided. Filtering of low energy and mobility electrons at the half-Heusler and full-Heusler interface along with the formation of Co interstitial defects in the half-Heusler matrix are proposed to be the possible causes for the enhanced Seebeck coefficient of the nano-precipitate containing specimen.

In this study, we investigate the effect of the heterogeneous micromechanical stress fields resulting from the grain-scale anisotropy on the redistribution of hydrogen using a diffusion coupled crystal plasticity model. A representative volume element with periodic boundary conditions was used to model a synthetic microstructure. The effect of tensile loading, initial hydrogen content and yield strength on the redistribution of lattice (C_L) and dislocation trapped (C_x) hydrogen was studied. It was found that the heterogeneous micromechanical stress fields resulted in the accumulation of both populations primarily at the grain boundaries. This shows that in addition to the well-known grain boundary trapping, the interplay of the heterogeneous micromechanical hydrostatic stresses and plastic strains contribute to the accumulation of hydrogen at the grain boundaries. Higher yield strength reduced the amount of C_x due to the resulting lower plastic deformation levels. On the other side, the resulting higher hydrostatic stresses increased the depletion of C_L from the compressive regions and its diffusion toward the tensile ones. These regions with increased C_L are expected to be potential damage initiation zones. This aligns with the observations that high-strength steels are more susceptible to hydrogen embrittlement than those with lower-strength.

A combined density functional theory and molecular dynamics approach is employed to study modifications of graphene at atomistic level for better H₂ storage. The study reveals H₂ desorption from hydrogenated defective graphene structure, V₂₂₂, to be exothermic. H₂ adsorption and desorption processes are found to be more reversible for V₂₂₂ as compared to pristine graphene. Our study shows that V₂₂₂ undergoes brittle fracture under tensile loading similar to the case of pristine graphene. The tensile strength of V₂₂₂ shows slight reduction with respect to their pristine counterpart, which is attributed to the transition of sp² to sp³-like hybridization. The study also shows that the V₂₂₂ structure is mechanically more stable than the defective graphene structure without chemically adsorbed hydrogen atoms. The current fundamental study, thus, reveals the efficient recovery mechanism of adsorbed hydrogen from V₂₂₂ and paves the way for the engineering of structural defects in graphene for H₂ storage.

Half-Heusler semiconductors satisfying 18-electron rule typically display promising characteristics for thermoelectric applications. A persistent inconsistency between the type of charge carriers in some of these alloys as obtained from experiment and theory however casts serious doubt on the computational prediction of new and efficient half-Heusler alloys. To gain insights into the origin of this disparity, we have investigated the effect of intrinsic point defects on the electronic structure of four frequently studied half-Heusler alloys of the form XYZ with Y being Ni or Co. Using state-of-the-art ab initio calculations, our study reveals that interstitial Ni and Co are energetically most stable point defects in these alloys. Remarkably, interstitial defect modifies the location of the Fermi level inside the band gap as well as the value of the band gap, thereby bringing in close agreement with the corresponding experimental result. This work thus highlights the decisive role played by interstitial defects in thermoelectric half-Heusler alloys, which may open a new avenue for deliberately utilizing these defects as a strategy for tailoring electronic structure and hence the corresponding thermoelectric properties.

The aggregation behavior of asphaltene in aqueous solution is systematically investigated based on a classical molecular dynamics study. In this work, a novel approach is adopted in order to investigate the structural and dynamical properties of the asphaltene nanoaggregates using different water models. The end-to-end distance of the asphaltene molecule is probed in order to understand the aggregation behavior in aqueous solution. The accuracy of different water models, that is, simple point charge, TIP4P-D, and TIP5P, is thoroughly investigated. In order to probe the dynamical properties of the asphaltene nanoaggregates, the transport coefficients, namely, diffusion coefficient and shear viscosity, are computed. The obtained results highlight the importance of using the appropriate water model in order to accurately study the aggregation behavior of asphaltene in aqueous solution.