Nature Of Interatomic Interactions Research Articles

A stability analysis of choline chloride: urea deep eutectic solvent using density functional theory

Deep eutectic solvents (DES) are eutectic mixtures of hydrogen bond acceptors and hydrogen bond donors. The stability of DES depends on the nature of interatomic interactions during their structural formation. This study focuses on the structural analysis of choline chloride (ChCl)-urea DES system (molar ratio 1:2) at the atomic level using density functional theory.Both gauche- and trans-conformers of choline were considered for geometric optimization with chloride anion at various orientations. The most stable structure of each conformer was further considered with urea to optimize the DES structure. Energy Decomposition Analysis (EDA) study showed that the binding energy (ΔEbind) for gauche-DES was more negative (−82.59 kJ/mol) than trans-DES (−7.60 kJ/mol). This indicated lower bond strength in trans-DES, hence higher stability in gauche-DES. It also agrees with calculation by dispersion energy, the Bader’s atoms-in-molecules theory for electrostatic interactions, the frontier molecular orbital analysis and Non-Covalent Interactions (NCI) analysis.

Fundamental electronic structure and multiatomic bonding in 13 biocompatible high-entropy alloys

High-entropy alloys (HEAs) have attracted great attention due to their many unique properties and potential applications. The nature of interatomic interactions in this unique class of complex multicomponent alloys is not fully developed or understood. We report a theoretical modeling technique to enable in-depth analysis of their electronic structures and interatomic bonding, and predict HEA properties based on the use of the quantum mechanical metrics, the total bond order density (TBOD) and the partial bond order density (PBOD). Application to 13 biocompatible multicomponent HEAs yields many new and insightful results, including the inadequacy of using the valence electron count, quantification of large lattice distortion, validation of mechanical properties with experiment data, modeling porosity to reduce Young’s modulus. This work outlines a road map for the rational design of HEAs for biomedical applications.

Origin of electronic properties of α-Hg3S2Cl2 polymorph

To investigate the energy bands structure of α-Hg 3 S 2 Cl 2 , first-principles calculations were performed within the density functional theory formalism using the SIESTA software package. Using the local density approximation the atomic positions are relaxed so as to minimize the forces acting on the atoms. The analysis of band energy dispersion shows that the VBM and CBM are located at Г symmetry point, resulting in a direct energy band gap of 3.198 eV. It is established that the nature of interatomic interactions has complex character and includes covalent and ionic parts. The inclusion of spin-orbit coupling not strongly modifies the structure of energy bands.

Isomorphism between ice and silica

Both ice and silica crystallize into solid-state structures composed of tetrahedral building units that are joined together to form an infinite four-connected net. Mathematical considerations suggest that there is a vast number of such nets and thus potential crystal structures. It is therefore perhaps surprising to discover that, despite the differences in the nature of interatomic interactions in these materials, a fair number of commonly observed ice and silica phases are based on common nets. Here we use computer simulation to investigate the origin of this symmetry between the structures formed for ice and silica and to attempt to understand why it is not complete. We start from a comparison of the dense phases and then move to the relationship between the different open (zeolitic and clathratic) structures formed for both materials. We show that there is a remarkably strong correlation between the energetics of isomorphic silica and water ice structures and that this correlation arises because of the strong link between the total energy of a material and its local geometric features. Finally, we discuss a number of as yet unsynthesized low-energy structures which include a phase of ice based on quartz, a silica based on the structure of ice VI, and an ice clathrate that is isomorphic to the silicate structure nonasil.

The behavior of the inter-ionic potential of condensed liquid cesium in a wide temperature range

The electronic structure of the liquid alkali metals depends strongly on their thermodynamic state. Here a modified pseudo-potential model has been applied to investigate the behavior of the inter-ionic potential of condensed liquid cesium from its melting point to the metal non-metal transition region. The parameters of the potential model are obtained from the experimental thermophysical data with a simple statistical mechanical model and some thermodynamic arguments. In low temperatures, the resulted inter-ionic potentials have a good behavior in the short range and contain the characteristic long range oscillations quite well. By increasing the temperature, the long range oscillations begin to disappear gradually. This behavior might be attributed to the change in the nature of inter-atomic interactions as a result of the localization of the valence electrons.

Effect of Lattice Vacancies on the Band Structure of the Ag[sub 5]Pb[sub 2]O[sub 6] Ternary Oxide

The effect of structural vacancies in the silver sublattice on the band structure and on the nature of interatomic interactions in the ternary oxide Ag5Pb2O6 is discussed in terms of the results of self-consistent full-potential linearized muffin-tin orbital (LMTO) calculations.

Quantum-chemical simulation of the electronic structure and chemical bonding in the new ‘superstoichiometric’ titanium carbonitride Ti 2CN 4

The electronic properties and the nature of interatomic interactions in the new 'superstoichiometric' metal-like titanium carbonitride Ti2CN4 with the spinel structure have been predicted using the ab initio DFT-DV calculaions of large clusters.

The Physics of Molten Silicates: From Simple Systems to Natural Magma

As witnessed at the beginning of the century by systematic determinations of silicate phase diagrams, the relevance of magma physics to igneous petrology has long been recognized. Until a couple of decades ago, however, the measurement and interpretation of physical properties of silicate melts were neglected by Earth scientists. This contrasted with the extensive work made by physical chemists, metallurgists and ceramists. The situation changed dramatically in the early 70's when Bottinga and Weill published seminal papers showing that both the density and viscosity of molten silicates could be accurately predicted as a function of temperature and composition from the experimental data gathered for a limited number of simple systems. Beginning in Carmichael's laboratory, much experimental and modelling effort has then been made to satisfy the diversi ty of geochemical needs. For the density of melts, subsequent models represent simple, successful extensions of Bottinga and Weill 's empirical work in terms of temperature or composition ranges. For the viscosity, in contrast, the complex composition and temperature dependences requires a firmer theoretical understanding to be accounted for quantitatively. If the so-called configurational entropy theory appears to provide such a theoretical framework, it remains to work out the composition dependence of the configurational entropy. For other properties such as the heat capacity or the compressibility, available models of prediction give various degrees of precision. In this paper, an attempt will be made to rationalize the reasons for the successes and limitations of these models. Critical in this respect are the configurational properties that are linked to the temperature-dependent structure of melts. The rote of short and medium range order will be discussed, along with the basically pairwise nature of interatomic interactions. Also discussed will be the difficulties of entropy modelling for systems where speciation is unknown and mixing is not ideal.

The electron structure and interatomic interactions in the bp xas 1−x system

The electron spectrum of the valence zone and the nature of interatomic interactions between the components of the semiconducting quasibinary BP-BAs system were studied by X-ray spectroscopy. The X-ray emission K and L spectra of the valence states of the components of BP and BAs and the four compositions of their solid solutions were obtained. The X-ray spectra of the valence bands of binary (BP and BAs) and ternary (BPAs) systems were interpreted by approximating the dipole selection rules; the phosphorus bands indicate the distribution of the s symmetry states, whereas the K bands of phosphorus and boron represent the distribution of p symmetry states of the corresponding components in the valence zone of the compounds. The initial structure of the spectra in the valence zone of boron and phosphorus in BP showed the presence of bonds only between two partners, B and P, which expressed themselves in the P 3s, p-B 2p interactions (first subzone), the B 2s-P 3ps interactions (second subzone) and the P 3p-B 2p interactions (third and fourth subzones of the valence zone). However, in the spectra of the solid BP x As 1− x solutions, an additional structure appeared both in the boron spectra showing interactions between boron and arsenic and in the phosphorus spectra showing interactions between phosphorus and arsenic.

Magnetic susceptibility calculation of semiconductor compounds AIIIBV in the MOLCAO approximation

AbstractA semiempirical model for calculating magnetic susceptibility, which allows to substantiate the magnetic susceptibility dependence on the crystal symmetry and the nature of interatomic interaction in it, has been proposed. Diamagnetic term of magnetic susceptibility in one electron approximation together with radius mean square of atoms in the AIIIBV compound is shown to be determined by the distance, position of gravity center of charge cloud, the degree of covalency of the compound and the overlapping integrals. Paramagnetic term of magnetic susceptibility in the approximation of the first coordination sphere is determined by the averaged transition energy between the excited and unexcited p‐levels of the system, the bond nature in a semiconductor and the overlapping integrals. Numerical results satisfactorily agree with the experimental data.

Study of Diffusion and Evaporation Parameters of a PtFe Alloy

A study is made of thermodynamic characteristics of the PtFe alloy prepared under maximum pure conditions. Using the method of simultaneous determining of diffusion coefficient and vapour elasticity results are obtained which are discussed in connection with the nature of interatomic interaction in the pointed types of alloys. [Russian Text Ignored].