A critical thermodynamic assessment of the Mg–Ni, Ni–Y binary and Mg–Ni–Y ternary systems

A thorough review and critical evaluation of phase equilibria and thermodynamic data for the phases in the Mg–Ni–Y ternary system have been carried out over the entire composition range from room temperature to above the liquidus. This system is being modeled for the first time using the modified quasichemical model which considers the presence of short range ordering in the liquid. The Gibbs energies of the different phases have been modeled, and optimized model parameters that reproduce all the experimental data simultaneously within experimental error limits have been obtained. For the liquid phases, the modified quasichemical model is applied. A sublattice model within the compound-energy formalism is used to take proper account of the structures of the binary intermediate solid solutions. The Mg–Ni and Ni–Y binary systems have been re-optimized based on the experimental phase equilibrium and thermodynamic data available in the literature. The optimized thermodynamic parameters for the Mg–Y system are taken from the previous thermodynamic assessment of the Mg–Cu–Y system by the same authors. The constructed database has been used to calculate liquidus projection, isothermal and vertical sections which are compared with the available experimental information on this system. The current calculations are in a good agreement with the experimental data reported in the literature.     

A thermodynamic description of the Al–Be system: Modeling and experiment

The Al–Be system is investigated via three steps. In the first step, all of the experimentally measured phase diagram and thermodynamic data available in the literature are critically reviewed. On the basis of the assessed phase diagram, in the second step, eight decisive samples are prepared by arc melting of Al and Be pieces and annealing at 600 C for eight days. Water-quenched samples are analyzed using differential thermal analysis (DTA), X-ray diffraction (XRD), optical microscopy, and scanning electron microscopy (SEM) techniques. In the last step, an optimal thermodynamic data set for the Al–Be system has been obtained by considering the present experimental data and the reliable literature data. The calculated phase diagram and thermodynamic properties agree well with the accurate experimental values.     

RADMAP: Simple probes for rapid assessment of complex reactivity: A method and case studies on the reaction of hydrogen atoms with unsaturated organic molecules

RADMAP, an open source program, allows for rapid analysis and visualization of the earliest stages of reactions between any molecule and a monoatomic probe (i.e., H*, H⁺, H⁻, Br*, or any other monoatomic species) using ab initio methods. This program creates non-planar potential energy surfaces of the initial interaction between a molecule of interest and the monoatomic probe. These surfaces can be used to both predict the site of addition as well as provide a qualitative estimate for the relative proportion of the formation of adducts; therefore, it gives insight into both the reactivity and the kinetic stability of a molecule. The program presents a way to quickly predict the number of signals anticipated in transverse field muon spin resonance spectra as well as their relative intensities.     

Recognition of halides and Y-shaped oxoanions by carbonylchromium-based urea-like molecules: A theoretical analysis of hydrogen bonding modes

One of the major challenges in anion recognition is to design hosts that can be used to distinguish between anions of different shapes. Urea-based molecules are widely used in anion recognition because the pair of -NH groups acts as an electron acceptor. Although these hosts can bind to both spherical anions (halides) and Y-shaped anions (oxoanions), experimental evidence to date does not provide a clear picture of what differences in the nature of the hydrogen bonding interactions could be used to distinguish between anions of different shapes. Here, we use several computational topology analyses to study the non-covalent interactions between Cr(CO)₃-based organometallic urea-like hosts and halides and Y-shaped oxoanions. Our results suggest that the F⁻ and AcO⁻ anions are recognized experimentally due to a combination of strong interaction and large infrared (IR) shifts upon complexation, verifying the remarkable IR-reporting ability of the Cr(CO)₃ moiety and its potential applications in anion recognition. The lone pairs of the oxygen atom in Y-shaped oxoanions directly interact with the -NH groups of the hosts, while all the shell electrons of the halides participate as a group in the interaction; however, the relative contributions of electrostatic and charge-transfer interactions are quite similar for the two types of anions. This insight into the nature of the anion-host interactions can be used to provide guidance for the design of hosts that differentiate between anions.