Formation Of Ionic Crystals Research Articles

Impact of Solution {Ba2+}:{SO42-} on Charge Evolution of Forming and Growing Barite (BaSO4) Crystals: A ζ-Potential Measurement Investigation.

The impact of solution stoichiometry on formation of BaSO4 (barite) crystals and the development of surface charge was investigated at various predefined stoichiometries (raq = 0.01, 0.1, 1, 10, and 100, where raq = {Ba2+}:{SO42-}). Synthesis experiments and zeta potential (ζ-potential) measurements were conducted at a fixed initial degree of supersaturation (Ωbarite = 1000, where Ωbarite = {Ba2+}{SO42-}/Ksp), at circumneutral pH of ∼6, 0.02 M NaCl, and ambient temperature and pressure. Mixed-mode measurement-phase analysis light scattering (M3-PALS) showed that the particles stayed negative for raq < 1 during barite crystal formation and positive for raq > 1. At raq = 1, two populations with a positive or negative ζ-potential prevailed for ∼2.5 h before a population with a circumneutral ζ-potential (-10 to +10 mV) remained. We relate the observations of particle charge evolution to particle size and morphology evolution under the experimental conditions. Furthermore, we showed that the ζ-potential became more negative when the pH was increased for every raq. In addition, our results demonstrated that the type of monovalent background electrolyte did not influence the ζ-potential of barite crystals significantly, although NaCl showed slightly different behavior compared to KCl and NaNO3. Our results show the important role of surface charge (evolution) during ionic crystal formation under nonstoichiometric conditions. Moreover, our combined scanning electron microscopy and ζ-potential results imply that the surface charge during particle formation can be influenced by solution stoichiometry, besides the pH and ionic strength, and may aid in predicting the fate of barite in environmental settings and in understanding and improving industrial barite (surface chemistry) processes.

Self-Assembly of Metal Oxide Nanoparticles in Liquid Metal toward Nucleation Control for Graphene Single-Crystal Arrays

Summary We have achieved the spontaneous assembly of alumina nanoparticles on a liquid metal surface and further synthesized a very-large-scale graphene single-crystal array. The effective electrical field established as a result of the electrical charge of the alumina nanoparticles in the liquid metal ensures the ordered self-assembly of the alumina islands and lays the foundation for precise spatial control of graphene nucleation, leading to the formation of graphene single-crystal arrays. In addition, controlling the density of the alumina in the liquid metal can precisely tune the periodicity of the arrays. This simple strategy, which is unlike the usual solid/aqueous solution system, opens up new territory for nanoparticle assembly. Focusing on the origin of the nanoparticle interaction that drives the self-assembly of ordered structure in the liquid metal system is a promising avenue for triggering more interesting applications.

Applying electric field to charged and polar particles between metallic plates: Extension of the Ewald method

We develop an efficient Ewald method of molecular dynamics simulation for calculating the electrostatic interactions among charged and polar particles between parallel metallic plates, where we may apply an electric field with an arbitrary size. We use the fact that the potential from the surface charges is equivalent to the sum of those from image charges and dipoles located outside the cell. We present simulation results on boundary effects of charged and polar fluids, formation of ionic crystals, and formation of dipole chains, where the applied field and the image interaction are crucial. For polar fluids, we find a large deviation of the classical Lorentz-field relation between the local field and the applied field due to pair correlations along the applied field. As general aspects, we clarify the difference between the potential-fixed and the charge-fixed boundary conditions and examine the relationship between the discrete particle description and the continuum electrostatics.

Evaluation of the role of “dilution” in ionic crystal formation by analysis of electron density distribution for two solvatomorphs of 4-amino-3,5-dinitropyrazole ammonium salt

The influence of “dilution” on the peculiarities of supramolecular organization in ionic crystals was analyzed by a detailed analysis of the electron density distribution function recovered by high-resolution X-ray diffraction experiments for two solvatomorphs of 4-amino-3,5-dinitropyrazole ammonium salt. The obtained results show that a decrease in the number of solvate water molecules unexpectedly increases the contribution from the anion-anion interactions to the lattice energy mainly due to the interactions between the π-systems of anions and between the nitro groups, which additionally confirms their binding nature. The latter indicates the general character of tendencies observed for hydrogen bonds and van der Waals interactions in the formation of crystalline materials in molecular and ionic crystals.

The Growth of Ionic Crystals Based on the Halogenation of Copper Cluster Anions

We investigated the halogenation reactivity of copper cluster anions produced via a magnetron-sputter source after introduction into a fast-flow tube reaction apparatus simultaneously with chlorine gas. Interesting cluster products corresponding to [Cu(n)Cl(n+1)](-) (n = 1-6) were observed with notable stability, and the mass distribution of these clusters exhibits an exponential decay with increasing values of n. Reaction kinetics analysis is provided on the gas-phase reactivity of copper cluster anions with chlorine. First-principle calculations suggest a series of cubic-like structures for these species similar to the structure of alkali halide clusters due to their similar electronic configurations. These structures act as a starting point in the formation of ionic crystals.

Structures and Sorption Properties of Ionic Crystals of Polyoxometalates with Macrocation

Abstract Polyoxometalates are nanosized metal–oxygen macroanions and suitable building blocks of ionic crystals with nanostructures in combination with appropriate macrocations. In this review, (1) formation of ionic crystals by the complexation of the polyoxometalates with a macrocation and the hydrophilic guest sorption properties, (2) effects of charges of polyoxometalates on the structures and sorption properties of ionic crystals, and (3) construction of both hydrophilic and hydrophobic channels in the crystal lattice of the polyoxometalate based ionic crystals are highlighted.

Effect of space discretization on phase diagrams in ionic systems: a field-theoretic approach.

Using Landau-Ginzburg-Wilson field-theoretic methods we determine for what kind of space discretization the transition between charge-disordered and charge-ordered phases in the restricted primitive model is fluctuation-induced first order. We identify this transition with ionic-crystal formation. We predict four types of generic phase diagrams in ionic systems for various kinds of space discretization for low and intermediate densities of ions. Our results also shed light on the simulation results obtained for an off-lattice ionic system over a wide range of densities, including the fcc crystal.