Inorganic Ionic Crystals Research Articles

Kaya's composite descriptor and Maximum Composite Hardness Rule for chemical reactions

Within the framework of Maximum Hardness and Minimum Polarizability Principles and as compatible with Jenkins Volume Based Thermodynamics approach, Kaya and coworkers calculated the lattice energies of inorganic ionic crystals using their ηM/Vm1/3 ratio (here ηM and Vm represent the chemical hardness and molar volume of any molecule, respectively). This ratio is called as Kaya's composite descriptor. It is apparent that Kaya's composite descriptor can be considered in the analysis of the chemical stability of compounds and the directions of chemical reactions. In a recent paper, Szentpaly, Kaya and Karakuş proposed Maximum Composite Hardness Rule for solid state double exchange reactions. To see the validity in other reaction types also of Kaya's composite descriptor and Maximum Composite Hardness Rule, twenty-eight chemical reactions including especially organic molecules were investigated. Reactivity descriptors such as chemical hardness, molar volume, polarizability regarding reactants and products putting in an appearance were calculated at B3LYP/6-31++g (d, p) calculation level with the help of computational chemistry tools. The result showed that instead of using separately the chemical hardness, polarizability and molar volume concepts, the use of Kaya chemical reactivity approach will be more useful to predict whether the reactions are exothermic or endothermic. It can be concluded from here that new composite descriptors should be derived and used for the accurate prediction of the reactivities of the chemical systems.

Two empirical formulae for estimating standard entropy of inorganic ionic solids and a possible connection between two associated electronic structure principles

Two empirical formulae for estimating the standard entropies of some inorganic ionic solids are proposed. Linear relations are suggested between the standard entropy and the cube root of the formula unit volume as well as the cube root of the diamagnetic susceptibility, building a bridge between conceptual density functional theory and solid state chemistry. It is noted that the stabilities of inorganic ionic crystals are closely related to their molar diamagnetic susceptibilities. The suggested correlation provides a connection between the maximum entropy and minimum magnetizability principles.

Intermolecular Interactions in Ionic Crystals of Nucleobase Chlorides—Combining Topological Analysis of Electron Densities with Energies of Electrostatic Interactions

Understanding intermolecular interactions in crystals of molecular ions continues to be difficult. On the one hand, the analysis of interactions from the point of view of formal charges of molecules, similarly as it is commonly done for inorganic ionic crystals, should be performed. On the other hand, when various functional groups are present in the crystal, it becomes natural to look at the interactions from the point of view of hydrogen bonding, π…π stacking and many other kinds of non-covalent atom–atom bonding. Often, these two approaches seem to lead to conflicting conclusions. On the basis of experimental charge densities of cytosinium chloride, adeninium chloride hemihydrate, and guanine dichloride crystals, with the help of theoretical simulations, we have deeply analysed intermolecular interactions among protonated nucleobases, chloride anions and water molecules. Here, in the second paper of the series of the two (Kumar et al., 2018, IUCrJ 5, 449–469), we focus on applying the above two approaches to the large set of dimers identified in analysed crystals. To understand electrostatic interactions, we analysed electrostatic interaction energies (Ees) computed directly from molecular charge densities and contrasted them with energies computed only from net molecular charges, or from a sum of electric multipolar moments, to find the charge penetration contribution to Ees. To characterize non-covalent interactions we performed topological analyses of crystal electron densities and estimated their interaction energies (EEML) from properties of intermolecular bond critical points. We show that the overall crystal architecture of the studied compounds is governed by the tight packing principle and strong electrostatic attractions and repulsions between ions. Many ions are oriented to each other in a way to strengthen attractive electrostatic interactions or weaken strong repulsion, but not all of them. Numerous bond critical points and bond paths were found between ions, including nucleobase cations despite their overall repulsive interactions. It is clear there is no correlation between EEML and Ees. However, strong relation between EEML and the charge penetration component of Ees is observed. The relation holds regardless of interaction types or whether or not interacting molecules bear the same or opposite charges. Thus, a charge density-based approach for computing intermolecular interaction energies and the atom–atom approach to analyse non-covalent interactions do complement each other, even in ionic systems.

A novel lattice energy calculation technique for simple inorganic crystals

In this pure theoretical study, a hitherto unexplored equation based on Shannon radii of the ions forming that crystal and chemical hardness of any crystal to calculate the lattice energies of simple inorganic ionic crystals has been presented. To prove the credibility of this equation, the results of the equation have been compared with experimental outcome obtained from Born-Fajans-Haber- cycle which is fundamentally enthalpy-based thermochemical cycle and prevalent theoretical approaches proposed for the calculation of lattice energies of ionic compounds. The results obtained and the comparisons made have demonstrated that the new equation is more useful compared to other theoretical approaches and allows to exceptionally accurate calculation of lattice energies of inorganic ionic crystals without doing any complex calculations.

Cold Flow as Versatile Approach for Stable and Highly Luminescent Quantum Dot-Salt Composites.

Since the beginning of the 1980s, colloidally synthesized quantum dots (QDs) have been in the focus of interest due to their possible implementation for color conversion, luminescent light concentrators, and lasing. For all these applications, the QDs benefit from being embedded into a host matrix to ensure stability and usability. Many different host materials used for this purpose still have their individual shortcomings. Here, we present a universal, fast, and flexible approach for the direct incorporation of a wide range of QDs into inorganic ionic crystals using cold flow. The QD solution is mixed with a finely milled salt, followed by the removal of the solvent under vacuum. Under high pressure (GPa), the salt powder loaded with QDs transforms into transparent pellets. This effect is well-known for many inorganic salts (e.g., KCl, KBr, KI, NaCl, CsI, AgCl) from, e.g., sample preparation for IR spectroscopy. With this approach, we are able to obtain strongly luminescent QD-salt composites, have precise control over the loading, and provide a chemically robust matrix ensuring long-term stability of the embedded QDs. Furthermore, we show the photo-, chemical, and thermal stability of the composite materials and their use as color conversion layers for a white light-emitting diode (w-LED). The method presented can potentially be used for all kinds of nanoparticles synthesized in organic as well as in aqueous media.

A Simple Method for the Calculation of Lattice Energies of Inorganic Ionic Crystals Based on the Chemical Hardness.

This paper presents a new technique for estimation of lattice energies of inorganic ionic compounds using a simple formula. This new method demonstrates the relationship between chemical hardness and lattice energies of ionic compounds. Here chemical hardness values of ionic compounds are calculated via our molecular hardness equation. The results obtained using the present method and comparisons made by considering experimental data and the results from other theoretical methods in the literature showed that the new method allows easy evaluation of lattice energies of inorganic ionic crystals without the need for ab initio calculations and complex calculations.

A stochastic principle behind polar properties of condensed molecular matter

A statistical mechanics view leads to the conclusion that polar molecules allowed to populate a degree of freedom for orientational disorder in a condensed phase thermalize into a bi-polar state featuring zero net polarity. In cases of orientational disorder polar order of condensed molecular matter can only exist in corresponding sectors of opposite average polarities. Channel type inclusion compounds, single component molecular crystals, solid solutions, optically anomalous crystals, inorganic ionic crystals, biomimetic crystals and biological tissues investigated by scanning pyroelectric and phase sensitive second harmonic generation microscopy all showed domains of opposite polarities in their final grown state. For reported polar molecular crystal structures it is assumed that kinetic hindrance along one direction of the polar axis is preventing the formation of a bi-polar state, thus allowing for a kinetically controlled mono-domain state. In this review we summarize theoretical and experimental findings leading to far reaching conclusions on the polar state of solid molecular matter. “… no stationary state … of a system has an electrical dipole moment.” P. W. Anderson, Science, 1972, 177, 393.

Inverse and High CO2/C2H2 Sorption Selectivity in Flexible Organic–Inorganic Ionic Crystals

Inverse and High CO₂/C₂H₂ Sorption Selectivity in Flexible Organic–Inorganic Ionic Crystals

Inverse and High CO2/C2H2 Sorption Selectivity in Flexible Organic–Inorganic Ionic Crystals

Highly selective CO2 sorption and inverse CO2/C2H2 sorption selectivity (4.8 at 278 K, 100 kPa) were achieved with an organic–inorganic ionic crystal. The key for the high affinity toward CO2 is the combination of structural flexibility and strong binding sites (K+) characteristic of organic–inorganic ionic crystals.

Zeotype Organic–Inorganic Ionic Crystals: Facile Cation Exchange and Controllable Sorption Properties

Size-selective sorption is exhibited by a zeotype organic–inorganic ionic crystal with 1D channels: the guest-free phase sorbs water and methanol, while larger molecules are excluded. Moreover, K+ ions, which reside in the channels (see picture; O red, C black, H pink, N blue), can be exchanged with other alkali metal ions, and the guest sorption properties depend on the type of alkali metal ions.

Zeotype Organic–Inorganic Ionic Crystals: Facile Cation Exchange and Controllable Sorption Properties

Zeotype Organic–Inorganic Ionic Crystals: Facile Cation Exchange and Controllable Sorption Properties

Fundamental studies of laser desorption from modified surfaces of ionic single crystals

The observation of photoinduced electron and ion emissions from a variety of wide bandgap insulators under UV and/or IR irradiation suggest that these materials typically possess occupied electronic defect states in the band gap. We have investigated the consequences of a variety of defect-generating stimuli (electron irradiation, laser irradiation, mechanical treatments and heating) on electron and ion emission from inorganic ionic crystals. These stimuli generate defects that strongly interact with the probe laser on a wide variety of ionic crystals. These stimuli dramatically decrease the probe laser intensities required for ion and neutral emissions, laser damage, and plume formation. We reference a number of these effects and illustrate a selected few on one material namely single crystal NaNO3.

Consequences of combining laser irradiation with other stimuli on laser desorption and ablation from wide bandgap insulators

When a transparent, wide bandgap insulator is exposed to sub-bandgap laser irradiation, defects at and near the surface often dominate the response in terms of particle emission and eventual ablation of material. We explored the consequences of applying a variety of stimuli that can generate defects on single crystal surfaces of inorganic ionic crystals. The stimuli include: electron beam irradiation, a second laser beam, mechanical treatment, and thermal treatment. We found that a common theme evolves where these stimuli generate sites for strong interactions of the probing laser beam, leading to a dramatic decrease in the laser intensities needed for ejection of ions, neutrals, and eventual plume formation.

When A Mild Mannered 1-5 eV Photon Meets A Big 10 eV Bandgap: Studies Of Laser Desorption From Modified Surfaces of Ionic Single Crystals

AbstractExposing wide-bandgap ionic materials to UV and IR photons can produce ion emissions with kinetic energies of several eV, well in excess of the photon energy. Electron emissions are also observed. This implies that these materials possess occupied electronic defect states within the band gap. We have investigated the consequences of a variety of defect-generating stimuli (electron irradiation, laser irradiation, mechanical treatments, and heating) on electron and ion emission from inorganic ionic crystals. These stimuli generate defects that strongly interact with the probe laser on a wide variety of ionic crystals, and dramatically decrease the probe laser intensities required for ion and neutral emissions, laser damage, and plume formation.

Absolute optical chirality of dirubidium (+)-tartrate and dicaesium (+)-tartrate crystals

The crystal structures and absolute optical chiralities of Rb2[(2R,3R)-C4H406], RBT (Mr=31901) and Cs2[(ER,3R)-C4H406], CST (Mr = 413.88) have been determined. For crystals grown from aqueous solutions containing (+)-tartrate ions the specific rotation was observed to be laevo over the visiblewavelength range along the optic axis and the space group was found to be P3221 (D 6) in both cases. Crystal data at 298K, CuKa, A=l.54178/k; for RBT: a=7.168(1), c=13.097(1)A, V= 582-8 (2) A 3, Z = 3, Dx = 2.726, D,,, = 2.727 (3) Mg m -3, ~ = 16.61 mm-I, F(000) = 450, final R--0.0281 and wR = 0.0572 for 804 unique observed reflections; for CST: a= 7.432 (2), c = 13.526 (3) A, V = 647.0 (5) ,~3, Z = 3, Dx = 3.187 Mg m -3, /x --- 67.56 mm- 1, F(000) = 558, final R = 0.0348 and wR = 0.0521 for 837 unique observed reflections. The relationship between optical rotation and structural chirality has been traced by following the rules established earlier for inorganic ionic crystals. It is shown that in the reported structures the intermolecular helical atomic arrangement of highly polarizable atoms (mainly oxygens and cations) rather than the contribution from the individual optically active organic molecules is responsible for optical rotation of the crystals. Special attention is paid to possible hydrogen bonds, both inter- and intramolecular, as they significantly influence the shape of the helices. The refractive indices and rotatory power, calculated from the structural data using a point-dipole polarizability theory, agree with the experimental results and support this point of view. Evidence is found that in concentrated solution RBT molecules also form helical arrangements.

Energy Exchange Processes

It is interesting to review the types of energy transfer process shown by different systems. By energy transfer, I mean the coupling mechanism between two parts of the system. I shall not go into the question of energy migration, which involves a knowledge of the relaxation around the excited unit of the crystal. The rare-gas crystal is a very simple molecular crystal, although, as Dr. Knox has shown, it may not be so simple electronically as some organic crystals like anthracene. Inorganic ionic crystals have a range of binding types much wider than organic molecular crystals do, and at the same time there is a much wider variety of energy transfer phenomena. It will be interesting here to present several examples from these different categories and to compare them. A classification scheme which is useful in making these comparisons is to divide the examples into those having overlapping and those having nonoverlapping charge distributions (1). In the second class, we may have spherically connected or not spherically connected charge distributions. By this is meant that a sphere of minimum size can be drawn about each charge distribution, and these spheres may or may not intersect. The case where the charge distributions do not overlap and are not spherically connected is the easiest one to treat mathematically. In this case, the interaction energy reduces to that of a set of classical point multipoles, as long as exchange can be neglected. This state of affairs seems to be a relatively good description of the organic molecular crystal. Davydov splitting can be described in terms of dipoledipole (2) or octupole-octupole coupling (3), and intensity anomalies due to the crystalling state can be similarly accounted for-with the addition of the dipoleoctupole interaction (4) in some cases. Some molecules are also able to be treated as a collection of nearly nonoverlap-