Showing papers on "Ionic bonding published in 2008"
TL;DR: These efforts to build better models of the monovalent ions within the pairwise Coulombic and 6-12 Lennard-Jones framework are described, where the models are tuned to balance crystal and solution properties in Ewald simulations with specific choices of well-known water models.
Abstract: Alkali (Li+, Na+, K+, Rb+, and Cs+) and halide (F−, Cl−, Br−, and I−) ions play an important role in many biological phenomena, roles that range from stabilization of biomolecular structure, to influence on biomolecular dynamics, to key physiological influence on homeostasis and signaling. To properly model ionic interaction and stability in atomistic simulations of biomolecular structure, dynamics, folding, catalysis, and function, an accurate model or representation of the monovalent ions is critically necessary. A good model needs to simultaneously reproduce many properties of ions, including their structure, dynamics, solvation, and moreover both the interactions of these ions with each other in the crystal and in solution and the interactions of ions with other molecules. At present, the best force fields for biomolecules employ a simple additive, nonpolarizable, and pairwise potential for atomic interaction. In this work, we describe our efforts to build better models of the monovalent ions within t...
2,550 citations
TL;DR: In this paper, the adsorption energy, geometry, density of states (DOS), dipole moment, and work function of each adatom-graphene system were calculated using first-principles density-functional theory with the generalized gradient approximation.
Abstract: The adsorption of 12 different metal adatoms on graphene is studied using first-principles density-functional theory with the generalized gradient approximation. The adsorption energy, geometry, density of states (DOS), dipole moment, and work function of each adatom-graphene system are calculated. For the adatoms studied from groups I--III of the Periodic Table, the results are consistent with ionic bonding, and the adsorption is characterized by minimal change in the graphene electronic states and large charge transfer. For transition, noble, and group IV metals, the calculations are consistent with covalent bonding, and the adsorption is characterized by strong hybridization between adatom and graphene electronic states. For ionically bonded adatoms, the charge transfer is calculated quantitatively using two methods, one based on the DOS and the other based on the real-space-charge density. A variation in dipole moments and work-function shifts across the different adatoms is observed. In particular, the work-function shift shows a general correlation with the induced interfacial dipole of the adatom-graphene system and the ionization potential of the isolated atom.
1,217 citations
TL;DR: A review.
Abstract: A review. Physicochem. properties of ionic liqs. are discussed. Chem. and electrochem. reactivity in ionic liqs. is described including electrode reactions, electrode reaction kinetics, electrosynthesis, etc.
1,049 citations
TL;DR: In the last 30 years, research efforts by the scientific community intensified significantly, stemming from the pioneering work of Takahashi and co-workers, with the initial development of mixed ionic-electronic conducting (MIEC) oxides.
1,037 citations
TL;DR: This Review proposes--as a still-unproved hypothesis--that this ion-transfer mechanism may also explain the ubiquitous contact electrification ("static electricity") of materials, such as organic polymers, that do not explicitly have ions at their surface.
Abstract: This Review discusses ionic electrets: their preparation, their mechanisms of formation, tools for their characterization, and their applications. An electret is a material that has a permanent, macroscopic electric field at its surface; this field can arise from a net orientation of polar groups in the material, or from a net, macroscopic electrostatic charge on the material. An ionic electret is a material that has a net electrostatic charge due to a difference in the number of cationic and anionic charges in the material. Any material that has ions at its surface, or accessible in its interior, has the potential to become an ionic electret. When such a material is brought into contact with some other material, ions can transfer between them. If the anions and cations have different propensities to transfer, the unequal transfer of these ions can result in a net transfer of charge between the two materials. This Review focuses on the experimental evidence and theoretical models for the formation of ionic electrets through this ion-transfer mechanism, and proposes--as a still-unproved hypothesis--that this ion-transfer mechanism may also explain the ubiquitous contact electrification ("static electricity") of materials, such as organic polymers, that do not explicitly have ions at their surface.
829 citations
TL;DR: The results present a view of the ionic liquid-metal electrode interface having a very thin "double layer" structure where the ions form a single layer at the surface to screen the electrode charge, and raise many other fundamental questions as to the detailed nature of the interfacial structure and interpretations of both electrochemical and spectroscopic data.
Abstract: Room-temperature ionic liquids are a new class of liquids with many important uses in electrical and electrochemical devices. The liquids are composed purely of ions in the liquid state with no solvent. They generally have good electrical and ionic conductivity and are electrochemically stable. Since their applications often depend critically on the interface structure of the liquid adjacent to the electrode, a molecular level description is necessary to understanding and improving their performance. There are currently no adequate models or descriptions on the organization of the ions, in these pure ionic compounds, adjacent to the electrode surface. In normal electrolytic solutions, the organization of solvent and ions is adequately described by the Gouy-Chapman-Sterns model. However, this model is based on the same concepts as those in Debye-Huckel theory, that is a dilute electrolyte, where ions are well-separated and noninteracting. This is definitely not the situation for ionic liquids. Thus our goal was to investigate the ionic liquid-metal interface using surface-specific vibrational spectroscopy sum frequency generation, SFG. This technique can probe the metal-liquid interface without interference from the bulk electrolyte. Thus the interface is probed in situ while the electrode potential is changed. To compliment the vibrational spectroscopy, electrochemical impedance spectroscopy (EIS) is used to measure the capacitance and estimate the "double layer" thickness and the potential of zero charge (PZC). In addition, the vibrational Stark shift of CO adsorbed on the Pt electrode was measured to provide an independent measure of the "double layer" thickness. All techniques were measured as a function of applied potential to provide full description of the interface for a variety of imidazolium-based (cation) ionic liquids. The vibrational Stark shift and EIS results suggest that ions organize in a Helmholtz-like layer at the interface, where the potential drop occurs over the a range of 3-5 A from the metal surface into the liquid. Further, the SFG results imply that the "double layer" structure is potential-dependent; At potentials positive of the PZC, anions adsorbed to the surface and the imidazolium ring are repelled to orient more along the surface normal, compared with the potentials negative of the PZC, at which the cation is oriented more parallel to the surface plane and the anions are repelled from the surface. The results present a view of the ionic liquid-metal electrode interface having a very thin "double layer" structure where the ions form a single layer at the surface to screen the electrode charge. However, the results also raise many other fundamental questions as to the detailed nature of the interfacial structure and interpretations of both electrochemical and spectroscopic data.
446 citations
TL;DR: The effects of ion size asymmetry and short-range correlations on the electrical double layer in ionic liquids are studied: molecular dynamics simulations of a model ionic liquid between two "electrodes" and the differential capacitance of each as a function of the electrode potential is calculated.
Abstract: We study the effects of ion size asymmetry and short-range correlations on the electrical double layer in ionic liquids: we perform molecular dynamics simulations of a model ionic liquid between two “electrodes” and calculate the differential capacitance of each as a function of the electrode potential. The capacitance curve has an asymmetric “bell-shape” character, in qualitative agreement with recent experiments and the mean-field theory (MFT) which takes into account the limitation on the maximal local density of ions. The short-range ionic correlations, not included in the MFT, lead to an overscreening effect which changes radically the structure of the double layer at small and moderate charging. With the radius of cations taken to be twice as large as anions, the position of the main capacitance maximum is shifted positively from the potential of zero charge (PZC), as predicted by MFT. An extension of the theory (EMFT), however, reproduces the simulated capacitance curve almost quantitatively. Capac...
398 citations
TL;DR: It is shown that by decreasing the length of the nanopore, the ionic current and ionic selectivity become affected by processes outside the nanochannel, justifying the use of the simple one-dimensional approximation in many cases.
Abstract: There has been an increasing interest in single nanochannel ionic devices, such as ionic filters that control the type of transported ions and ionic diodes that rectify the ionic flow. In this article, we theoretically investigate the importance of the dimensions, surface charge, electrolyte concentration, and applied bias on nanopore performance. We compare numerical solutions of the Poisson, Nernst−Planck (PNP), and Navier−Stokes (NS) equations with their one-dimensional, analytical approximations. We show that by decreasing the length of the nanopore, the ionic current and ionic selectivity become affected by processes outside the nanochannel. The contribution of electroosmosis is noticeable, especially for highly charged nanochannels, but is insignificant, justifying the use of the simple one-dimensional approximation in many cases. Estimates for the critical electric field at which the nanopore selectivity decreases and the ion current starts to saturate are provided.
395 citations
TL;DR: In this article, the authors analyzed the double layer formation in room temperature ionic liquids and compared the results with the mean-field theory and the charge conservation law at large electrode polarizations.
387 citations
TL;DR: The first ansa-aminoborane N-TMPN-CH2C6H4B(C6F5)2 which is able to reversibly activate H2 through an intramolecular mechanism is synthesized and is employed in the catalytic reduction of nonsterically demanding imines and enamines under mild conditions to give the corresponding amines in high yields.
Abstract: The first ansa-aminoborane N-TMPN-CH2C6H4B(C6F5)2 (where TMPNH is 2,2,6,6-tetramethylpiperidinyl) which is able to reversibly activate H2 through an intramolecular mechanism is synthesized This new substance makes use of the concept of molecular tweezers where the active N and B centers are located close to each other so that one H2 molecule can fit in this void and be activated Because of the fixed geometry of this ansa-ammonium-borate it forms a short N−H···H−B dihydrogen bond of 178 A as determined by X-ray analysis Therefore, the bound hydrogen can be released above 100 °C In addition, the short H···H contact and the N−H···H (154°) and B−H···H (125°) angles show that the dihydrogen interaction in N-TMPNH-CH2C6H4BH(C6F5)2 is partially covalent in nature As a basis for discussing the mechanism, quantum chemical calculations are performed and it is found that the energy needed for splitting H2 can arise from the Coulomb attraction between the resulting ionic fragments, or “Coulomb pays for Heitler−
332 citations
TL;DR: In this paper, a review of the recent results in the field of metal-organic frameworks (MOFs) is presented, bringing together the systematic approaches with results obtained by serendipity to give an overview on current and future possibilities.
TL;DR: In this article, the authors developed a new composition of oxide proton conductor, Ba(Zr0.1Ce0.7Y0.2) O3 d (BZCY7), which exhibits not only adequate proton conductivity but also sufficient chemical and thermal stability over a wide range of conditions relevant to SOFC operation.
Abstract: The demand for clean, secure, and renewable energy has stimulated great interest in fuel cells. Among all types of fuel cells, solid oxide fuel cells (SOFCs) have attracted much attention because of its high energy efficiency, modularity, and excellent fuel flexibility; in fact, they are the only fuel cell system that has the potential for direct utilization (or through internal reforming) of readily available fuels, gasified coal gas, and renewable fuels. Unfortunately, the current SOFC systems are still too expensive for broad commercialization. To be economically competitive, the operating temperature has to be sufficiently low so that much less expensivematerials may be used. Compared with low-temperature SOFCs based on oxygen ion conductors (e.g., Gd-doped ceria or Y-stabilized zirconia), SOFCs based on oxide proton conductors offer several advantages. First, lower activation energy for proton than for oxygen ion transport implies that the ionic conductivities of proton conductors have less temperature dependence, potentially exhibiting higher ionic conductivities at intermediate or low temperatures. Second, the fuel will not be diluted during fuel cell operation since water is produced in the cathode compartment, not in the fuel side as does for an oxygen ion conductor-based SOFC. However, the development of low-temperature SOFCs based on oxide proton conductors is still in its infancy. While BaCeO3-based composition exhibits high ionic conductivity, they are not suitable for SOFC applications due to the instability in H2Oand CO2-containing atmospheres. [9,10] Secondly, electrolyte supported configuration was commonly adopted due to the requisite conditions for fabrication of these materials in the required form (e.g., the high sintering temperature). Recently, we have developed a new composition of oxide proton conductor, Ba(Zr0.1Ce0.7Y0.2) O3 d (BZCY7), in the Barium–Zirconium–Cerium–Yttrium family which exhibits not only adequate proton conductivity but also sufficient chemical and thermal stability over a wide range of conditions relevant to SOFC operation. A modified co-pressing and co-firing method was successfully developed to fabricate
TL;DR: This work is a review of the Poisson–Boltzmann (PB) continuum electrostatics theory and its modifications, with a focus on salt effects and counterion binding, and discusses the conventional PB equation, the corresponding functionals of the electrostatic free energy, including a connection to DFT.
Abstract: This work is a review of the Poisson-Boltzmann (PB) continuum electrostatics theory and its modifications, with a focus on salt effects and counterion binding. The PB model is one of the mesoscopic theories that describes the electrostatic potential and equilibrium distribution of mobile ions around molecules in solution. It serves as a tool to characterize electrostatic properties of molecules, counterion association, electrostatic contributions to solvation, and molecular binding free energies. We focus on general formulations which can be applied to large molecules of arbitrary shape in all-atomic representation, including highly charged biomolecules such as nucleic acids. These molecules present a challenge for theoretical description, because the conventional PB model may become insufficient in those cases. We discuss the conventional PB equation, the corresponding functionals of the electrostatic free energy, including a connection to DFT, simple empirical extensions to this model accounting for finite size of ions, the modified PB theory including ionic correlations and fluctuations, the cell model, and supplementary methods allowing to incorporate site-bound ions in the PB calculations.
TL;DR: Data and computed reaction barriers argue against mechanisms in which the haloarene reacts with a two-coordinate anionic copper species and mechanisms that start with electron transfer to generate a free iodoarene radical anion, which are more consistent with mechanisms involving cleavage of the carbon-halogen bond within the coordination sphere of the metal.
Abstract: Copper(I) imidate and amidate complexes of chelating N,N-donor ligands, which are proposed intermediates in copper-catalyzed amidations of aryl halides, have been synthesized and characterized by X-ray diffraction and detailed solution-phase methods. In some cases, the complexes adopt neutral, three-coordinate trigonal planar structures in the solid state, but in other cases they adopt an ionic form consisting of an L2Cu+ cation and a CuX2− anion. A tetraalkylammonium salt of the CuX2− anion in which X = phthalimidate was also isolated. Conductivity measurements and 1H NMR spectra of mixtures of two complexes all indicate that the complexes exist predominantly in the ionic form in DMSO and DMF solutions. One complex was sufficiently soluble for conductance measurements in less polar solvents and was shown to adopt some degree of the ionic form in THF and predominantly the neutral form in benzene. The complexes containing dative nitrogen ligands reacted with iodoarenes and bromoarenes to form products from...
TL;DR: A local model of pairing of ions from the solution with charged and polar groups at the protein surface is suggested, in analogy to the air/water interface.
Abstract: The surfaces of aqueous solutions are traditionally viewed as devoid of inorganic ions. Molecular simulations and surface-selective spectroscopic techniques show, however, that large polarizable anions and hydronium cations can be found (and even enhanced) at the surface and are involved in chemistry at the air/water interface. Here, we review recent studies of ions at the air/water interface and compare from this perspective water with other polar solvents. For water, we focus in particular on the surface behavior of its ionic product (i.e., hydronium and hydroxide ions). We also investigate the feasibility of dielectric models for the description of the protein/water interface, in analogy to the air/water interface. Little correlation is found between these two interfaces in terms of ion segregation. Therefore, we suggest a local model of pairing of ions from the solution with charged and polar groups at the protein surface. We also describe corresponding results of experimental studies on aqueous model systems.
TL;DR: In this article, two possible strategies for tuning the mechanical properties of cementitious materials by modifying the bonding scheme in the hydrates at molecular level are discussed, based on the strengthening of the network of cohesion forces acting between the individual C-S-H lamellae or between their crystallites.
TL;DR: Results show that most of these surfaces exhibit high protein resistance in a wide range of ionic strengths and are more effective than zwitterionic self-assembled monolayers.
TL;DR: It is shown that signatures of oxidation states and multivalence—such as X-ray photoemission core-level shifts, ionic radii and variations in local magnetization—that have often been interpreted as literal charge transfer are instead a consequence of the negative-feedback charge regulation.
Abstract: Transition-metal atoms embedded in an ionic or semiconducting crystal can exist in various oxidation states that have distinct signatures in X-ray photoemission spectroscopy and 'ionic radii' which vary with the oxidation state of the atom. These oxidation states are often tacitly associated with a physical ionization of the transition-metal atoms--that is, a literal transfer of charge to or from the atoms. Physical models have been founded on this charge-transfer paradigm, but first-principles quantum mechanical calculations show only negligible changes in the local transition-metal charge as the oxidation state is altered. Here we explain this peculiar tendency of transition-metal atoms to maintain a constant local charge under external perturbations in terms of an inherent, homeostasis-like negative feedback. We show that signatures of oxidation states and multivalence--such as X-ray photoemission core-level shifts, ionic radii and variations in local magnetization--that have often been interpreted as literal charge transfer are instead a consequence of the negative-feedback charge regulation.
TL;DR: Evaluated the transport and deposition behavior of carboxyl functionalized single-walled carbon nanotubes in a well-defined porous medium composed of clean quartz sand over a range of solution chemistries concludes that both physicochemical filtration and straining play a role at low (< 3.0 mM) ionic strength, while physicochemicalfiltration is the dominant mechanism of SWNT filtrations at higher ionic strengths.
Abstract: Deposition of nanomaterials onto surfaces is a key process governing their transport, fate, and reactivity in aquatic systems. We evaluated the transport and deposition behavior of carboxyl functionalized single-walled carbon nanotubes (SWNTs) in a well-defined porous medium composed of clean quartz sand over a range of solution chemistries. Our results showthat increasing solution ionic strength or addition of calcium ions result in increased SWNT deposition (filtration). This observation is consistent with conventional colloid deposition theories, thereby suggesting that physicochemical filtration plays an important role in SWNT transport. However, the relatively insignificant change of SWNT filtration at low ionic strengths (< or = 3.0 mM KCl) and the incomplete breakthrough of SWNTs in deionized water (C/Co = 0.90) indicate that physical straining also plays a role in the capture of SWNTs within the packed sand column. It is proposed that SWNT shape and structure, particularly the very large aspect ratio and its highly bundled (aggregated) state in aqueous solutions, contribute considerably to straining in flow through porous media. We conclude that both physicochemical filtration and straining play a role at low (< 3.0 mM) ionic strength, while physicochemical filtration is the dominant mechanism of SWNT filtration at higher ionic strengths. Our results further show that deposited SWNTs are mobilized (released) from the quartz sand upon introduction of low ionic strength solution following deposition experiments with monovalent salt (KCl). In contrast, SWNTs deposited in the presence of calcium ions were not released upon introduction of low ionic strength solution to the packed column, even when humic acid was present in solution during SWNT deposition.
TL;DR: In this paper, a volumetric analysis of the VLE data using an equation-of-state model has been performed, and the prediction for the VLLE has been confirmed experimentally, which indicates that CO2 may have formed a nonvolatile or very low vapor pressure molecular complex with the ionic liquid.
TL;DR: In this article, the behavior of vermiculite and montmorillonite toward adsorption of Cd2+, Pb2+, Zn2+, Mn2+, Cu2+ and Zn 2+ was compared.
TL;DR: It is shown that the water clusters are formed almost exclusively by linear chains of hydrogen-bonded molecules in the ionic liquid and its mixtures with water, from zero up to 0.5 mol fraction of water.
Abstract: We report on molecular dynamics simulations of the ionic liquid [bmim][BF4] and its mixtures with water, from zero up to 0.5 mol fraction of water. All of the simulations are carried out with two published force fields. The results are compared with each other and with published as well as new NMR data on the same mixtures, whenever possible. We perform extensive analyses of structural quantities, such as pair correlation functions, nearest-neighbor analysis and size distribution of the water clusters formed at higher concentrations. We show that the water clusters are formed almost exclusively by linear chains of hydrogen-bonded molecules. There is a nanoscale structuring of the mixtures but no macroscopic phase separation among the components, in agreement with experiment. Roughly, we identify two solvation regimes. At low water content, the ions are selectively coordinated by individual water molecules, but their ionic network is largely unperturbed. At high water content, the ionic network is somewhat...
TL;DR: In this article, the electronic structures of metal-rich binary phosphides M2P and M3P (M = Cr−Ni) have been examined by means of X-ray photoelectron and absorption spectroscopy and compared with those of the monophosphides MP.
Abstract: The electronic structures of metal-rich binary phosphides M2P and M3P (M = Cr−Ni) have been examined by means of X-ray photoelectron and absorption spectroscopy and compared with those of the monophosphides MP. The P 2p3/2 binding and P K-edge absorption energies decrease with greater ionic character of the M−P bonding and indicate the presence of anionic phosphorus, contrary to previous theoretical assertions but consistent with our previous results. Interatomic effects play a more important role in affecting the energy shifts in these metal-rich phosphides than in the monophosphides, becoming more pronounced with higher metal concentration. Although the M 2p3/2 XPS spectra show no discernible shifts in binding energies, they reveal satellite features whose intensity can be related to metal charge in the Co- and Ni-containing phosphides. In these cases, the metal charge becomes less positive with higher metal concentration. For Ni2P and Ni3P, this trend was confirmed from an analysis of the Ni L-edge and...
TL;DR: In this paper, a polymer electrolyte based on PVA doped with different concentrations of NH 4 Br has been prepared by solution casting technique and the complexation of the prepared polymer electrolytes has been studied using X-ray diffraction (XRD) and Fourier transform infra red (FTIR) spectroscopy.
Abstract: Polymer electrolyte based on PVA doped with different concentrations of NH 4 Br has been prepared by solution casting technique. The complexation of the prepared polymer electrolytes has been studied using X-ray diffraction (XRD) and Fourier transform infra red (FTIR) spectroscopy. The maximum ionic conductivity (5.7×10 −4 S cm −1 ) has been obtained for 25 mol% NH 4 Br-doped PVA polymer electrolyte. The temperature dependence of ionic conductivity of the prepared polymer electrolytes obeys Arrhenius law. The ionic transference number of mobile ions has been estimated by dc polarization method and the results reveal that the conducting species are predominantly ions. The dielectric behavior of the polymer electrolytes has been analyzed using dielectric permittivity and electric modulus spectra.
TL;DR: Two-dimensional vibrational spectroscopy results reveal that the ILs sense quite different environments during the whole dilution process, and the three-dimensional network structure of pure ILs was destroyed gradually into ionic clusters, then the clusters were further dissociated into ions surrounded by water molecules, and finally the latter became the dominant form in bulk water.
Abstract: Two-dimensional vibrational spectroscopy is applied to investigate the dilution process of 1-ethyl-3-methyl-imidazolium tetrafluoroborate ([Emim][BF4]) in water. With increasing water content in ionic liquid (IL)/water mixtures, the C−H stretching vibration of the imidazolium cation showed systematic blue-shifts, which reflect the weakening of the cohesion between the cation and anion of ILs. The two-dimensional IR results reveal that the ILs sense quite different environments during the whole dilution process. First, the three-dimensional network structure of pure ILs was destroyed gradually into ionic clusters, then the clusters were further dissociated into ionic pairs surrounded by water molecules, and finally the latter became the dominant form in bulk water. Within the concentration range we investigated (0.02 < XD2O < 0.90), the intruding water does not dissociate ILs into ions completely. The structure evolution of ILs can be clearly detected and visualized in the asynchronous spectrum.
TL;DR: For the aggregation mechanism in [C 2 mim][NTf(2], the reaction-limited cluster aggregation (RLCA) model was proposed by rheology and light scattering measurements, and exciting viscoelastic responses were found in all of the nanocomposite ion gels.
Abstract: The dispersion of silica nanoparticles made an ionic liquid, 1-ethyl-3-methyl imidazolium bis(trifluoromethanesulfonyl)amide ([C2mim][NTf2]), gelled even by the addition of 2−3 wt %, due to the formation of interconnected particulate silica networks in [C2mim][NTf2]. The ionic transport and viscoelastic properties of these nanocomposite ion gels were investigated in relation to the microstructure. Despite their solid-like behavior, the nanocomposite ion gels exhibited a high ionic conductivity of approximately 10−2 S cm−1 at 30 °C, which is comparable to that of neat [C2mim][NTf2]. Intriguing viscoelastic responses, such as shear-thinning and shear-induced sol−gel transitions, were found in all of the nanocomposite ion gels. By adjusting the silica concentration, the elastic modulus (G′) could be precisely controlled in a range of more than 3 orders of magnitude and reached approximately 106 Pa without a considerable decrease in the ionic conductivity; the characteristic viscoelastic response was also mai...
TL;DR: NIMs as mentioned in this paper are the first example of neat, self-suspended fluids of nanoparticles (i.e., in the absence of a suspending medium) and offer remarkable versatility for current and future applications.
Abstract: Within the general field of polymer grafted or “hairy” nanoparticles, nanoscale ionic materials (NIMs), consisting of a soft polymeric canopy bound to a well-defined nanoparticle core by an ionic bond, occupy a growing niche. They are the first example of neat, self-suspended fluids of nanoparticles (i.e., in the absence of a suspending medium). As such, the perennial dispersion challenges associated with polymer nanocomposites are minimized while the dynamic nature of the ionic bonds provides opportunities for self-healing behavior. Combining the properties of ionic liquids, charged colloid suspensions, and well-dispersed nanocomposites, this new materials platform offers remarkable versatility for current and future applications. This perspective covers techniques and current challenges in synthesis, discusses the state of understanding of the theory behind their structure and properties, and examines successes and future prospects in application in a number of areas, notably in energy-related technologies.
TL;DR: In this paper, the ionic and electronic conductivities as well as chemical Li-diffusivity in single crystalline LiFePO 4 as a function of crystallographic orientation over an extended temperature range were investigated.
TL;DR: The solubility of water and carbon dioxide in the ionic liquid 1-n-hexyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide ([hmim][Tf2N]) is computed using atomistic Monte Carlo simulations using newly developed biasing algorithm to enable complete isotherms to be computed.
Abstract: The solubility of water and carbon dioxide in the ionic liquid 1-n-hexyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide ([hmim][Tf2N]) is computed using atomistic Monte Carlo simulations. A newly developed biasing algorithm is used to enable complete isotherms to be computed. In addition, a recently developed pairwise damped electrostatic potential calculation procedure is used to speed the calculations. The computed isotherms, Henry's Law constants, and partial molar enthalpies of absorption are all in quantitative agreement with available experimental data. The simulations predict that the excess molar volume of CO2/ionic liquid mixtures is large and negative. Analysis of ionic liquid conformations shows that the CO2 does not perturb the underlying liquid structure until very high CO2 concentrations are reached. At the highest CO2 concentrations, the alkyl chain on the cation stretches out slightly, and the distance between cation and anion centers of mass increases by about 1 A. Water/ionic liqu...
TL;DR: In this paper, the authors analyzed the effect of three-layer insulating materials such as LiF, NaCl, MgO, CaS, and BaO on various (001) metal surfaces.
Abstract: Ultrathin dielectric films deposited on a metal surface induce variations in the work function that can be relevant for the final properties of the metal/oxide interface. In this work we analyze with the help of density-functional theory calculations the effect of depositing three-layer films of insulating materials such as LiF, NaCl, MgO, CaS, and BaO on various (001) metal surfaces. We found that the change in work function $\ensuremath{\Delta}\ensuremath{\Phi}$ is due to three main contributions: an electrostatic ``compression'' effect which dominates for highly ionic films such as LiF, a charge-transfer effect which is largest for less ionic films such as BaO, and the surface relaxation induced by the formation of the interface bond which largely depends on the lattice mismatch between the dielectric film and the metal. Finally, we propose a universal correlation between the work function change and the energy difference between the position of the Fermi level of the metal surface and the top of the valence band of the dielectric film.