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This study presents a microscopic model for the correlation between the concentration of oxygen vacancies and voltage suppression in high voltage spinel cathodes for Li-ion batteries. Using first principles simulations, it is shown that neutral oxygen vacancies in LiNi0.5Mn1.5O4- δ promote substitutional Ni/Mn disorder and the formation of Ni-rich and Ni-poor regions. The former trap oxygen vacancies, while the latter trap electrons associated with these vacancies. This leads to the creation of deep and shallow Mn3+ states and affects the stability of the lattice Li ions. Together, these two factors result in a characteristic profile of the voltage dependence on Li content. This insight provides guidance for mitigating the voltage suppression in LiNi0.5Mn1.5O4 and other cathodes. [ABSTRACT FROM AUTHOR]

Surfactants are widely used as templatesto control the nucleationand growth of nanostructured metal oxides such as titania. To gaininsight into the origin of the surfactant–titania interactionsresponsible for polymorph and orientation selection, we simulate theself-assembly of an anionic surfactant monolayer on various low-indextitania surfaces, for a range of densities. We characterize the bindingin each case and compute the adhesion energies, finding anatase (100)and rutile (110) to be the strongest-binding surfaces. The sodiumcounterions in the monolayer are found to dominate the adhesion. Itis also observed that the assembly is directed predominantly by surface-monolayerelectrostatic complementarity. Incorporating water displacement intothe calculations does not alter the general findings but does causethe adhesion energies to fall within a smaller range. [ABSTRACT FROM AUTHOR]

A microscopic model for voltage suppression in complex transition metal oxides is proposed by M. L. Sushko and co‐workers based on careful analysis of the electronic structure and electrostatic potential in one of the most promising cathode materials—LiNi0.5Mn1.5O4—as a case study. On page 5530, ab initio simulations reveal that the electrochemical performance of LiNi0.5Mn1.5O4 and similar transition metal oxides can be finely tuned by controlling the concentration of oxygen vacancies. [ABSTRACT FROM AUTHOR]

The article discusses computation techniques at the organic-inorganic interface in biomineralization. The mineralization process is controlled by an insoluble organic matrix, usually containing macromolecules, glycans and polysaccharides. The article discusses the use of quantum mechanics and molecular mechanics to study biomineralization at the organic-inorganic interface.

This study presents a microscopic model for the correlation between the concentration of oxygen vacancies and voltage suppression in high voltage spinel cathodes for Li-ion batteries. Using first principles simulations, it is shown that neutral oxygen vacancies in LiNi0.5Mn1.5O4- δ promote substitutional Ni/Mn disorder and the formation of Ni-rich and Ni-poor regions. The former trap oxygen vacancies, while the latter trap electrons associated with these vacancies. This leads to the creation of deep and shallow Mn3+ states and affects the stability of the lattice Li ions. Together, these two factors result in a characteristic profile of the voltage dependence on Li content. This insight provides guidance for mitigating the voltage suppression in LiNi0.5Mn1.5O4 and other cathodes. [ABSTRACT FROM AUTHOR]

Efficient removal of heterocyclic organosulfur compounds from fuels can relieve increasingly serious environmental problems (e.g., gas exhaust contaminants triggering the formation of acid rain that can damage fragile ecological systems). Toward this end, novel metal‐organic frameworks (MOFs)‐based sorbent materials are designed and synthesized with distinct hard and soft metal building units, specifically {[Yb6Cu12(OH)4(PyC)12(H2O)36]·(NO3)14·xS}n (QUST‐81) and {[Yb4O(H2O)4Cu8(OH)8/3(PyC)8(HCOO)4]·(NO3)10/3·xS}n (QUST‐82), where H2PyC = 4‐Pyrazolecarboxylic acid. Exploiting the hard/soft duality, it is shown that the more stable QUST‐82 can preserve desulfurization efficiency in the presence of competing nitrogen‐containing contaminate. In addition, thermodynamically controlled single‐crystal‐to‐single‐crystal (SC–SC) phase transition is uncovered from QUST‐81 to QUST‐82, and in turn, mechanistic features are probed via X‐ray diffraction, inductively coupled plasma atomic emission spectroscopy, and ab initio molecular dynamics simulations. Thermodynamically controlled hetero‐metallic metal‐organic frameworks (MOFs) are able to preserve the desulfurization efficiency in the presence of competing nitrogen contaminate. The preserved adsorption capacity for organosulfur is shown to originate from the dual hard/soft Lewis acid nature in the heterometallic MOF. [ABSTRACT FROM AUTHOR]

Surface passivation, a desirable natural consequence during initial oxidation of alloys, is the foundation for functioning of corrosion and oxidation resistant alloys ranging from industrial stainless steel to kitchen utensils. This initial oxidation has been long perceived to vary with crystal facet, however, the underlying mechanism remains elusive. Here, using in situ environmental transmission electron microscopy, we gain atomic details on crystal facet dependent initial oxidation behavior in a model Ni-5Cr alloy. We find the (001) surface shows higher initial oxidation resistance as compared to the (111) surface. We reveal the crystal facet dependent oxidation is related to an interfacial atomic sieving effect, wherein the oxide/metal interface selectively promotes diffusion of certain atomic species. Density functional theory calculations rationalize the oxygen diffusion across Ni(111)/NiO(111) interface, as contrasted with Ni(001)/NiO(111), is enhanced. We unveil that crystal facet with initial fast oxidation rate could conversely switch to a slow steady state oxidation., (© 2024. The Author(s).)

Many important chemical processes involve reactivity and dynamics in complex solutions. Gaining a fundamental understanding of these reaction mechanisms is a challenging goal that requires advanced computational and experimental approaches. However, important techniques such as molecular simulation have limitations in terms of scales of time, length, and system complexity. Furthermore, among the currently available solvation models, there are very few designed to describe the interaction between the molecular scale and the mesoscale. To help address this challenge, here, we establish a novel hybrid approach that couples first-principles plane-wave density functional theory with classical density functional theory (cDFT). In this approach, a region of interest described by ab initio molecular dynamics (AIMD) interacts with the surrounding medium described using cDFT to arrive at a self-consistent ground state. cDFT is a robust but efficient mesoscopic approach to accurate thermodynamics of bulk electrolyte solutions over a wide concentration range (up to 2M concentrations). Benchmarking against commonly used continuum models of solvation, such as SMD, as well as experiments, demonstrates that our hybrid AIMD-cDFT method is able to produce reasonable solvation energies for a variety of molecules and ions. With this model, we also examined the solvent effects on a prototype SN2 reaction of the nucleophilic attack of a chloride ion on methyl chloride in the solution. The resulting reaction pathway profile and the solution phase barrier agree well with experiment, showing that our AIMD/cDFT hybrid approach can provide insight into the specific role of the solvent on the reaction coordinate., (© 2024 Author(s). All article content, except where otherwise noted, is licensed under a Creative Commons Attribution (CC BY) license (http://creativecommons.org/licenses/by/4.0/).)

SignificanceMany crystallization processes occurring in nature produce highly ordered hierarchical architectures. Their formation cannot be explained using classical models of monomer-by-monomer growth. One of the possible pathways involves crystallization through the attachment of oriented nanocrystals. Thus, it requires detailed understanding of the mechanism of particle dynamics that leads to their precise crystallographic alignment along specific faces. In this study, we discover a particle-morphology-independent oriented attachment mechanism for hematite nanocrystals. Independent of crystal morphology, particles always align along the [001] direction driven by aligning interactions between (001) faces and repulsive interactions between other pairs of hematite faces. These results highlight that strong face specificity along one crystallographic direction can render oriented attachment to be independent of initial particle morphology.

ZIF-8 was synthesized in supercritical carbon dioxide (scCO 2 ). In situ powder X-ray diffraction, ex situ microscopy, and simulations provide an encompassing view of the formation of ZIF-8 and intermediary ZnO@ZIF-8 composites in this nontraditional solvent. Time-resolved imaging exposed divergent physicochemical reaction pathways from previous studies of the growth of anisotropic ZIF-8 core@shell structures in traditional solvents. Synthetically relevant physiochemical properties of scCO 2 were integrated into classical nucleation theory, relating interfacial forces, calculated through DFTB+ based molecular dynamics (MD), with 3D nucleation outcomes. The kinetics of crystallization were examined and displayed a characteristic signature of time- and temperature-dependent mechanisms over the extent of the reaction. Lastly, it is shown that subtle factors, such as the extent of reaction and the size/shape of sacrificial templates can tailor ZIF-8 composition and size, eliciting control over hierarchical porosity in a nonconventional green solvent., (© 2020 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)