Software Products for the Numeric Evaluation of Oscillation of Nox in the Pulverized Fuel Combustor

In this paper, a numerical study of the formation of nitrogen oxides in the combustion chamber based on the model created by Mitchellom and Terbellom. The distribution of furnace temperature and the concentration of nitrogen oxides, as well as a comparison of numerical results with the data of field experiment

Principle of electronegativity. State-of-the art

Modern views on atomic and group electronegativity are classified. Trends in the electronegativity concept development are analysed. Special attention is paid to the latest approaches to the electronegativity determination such as concept of an «orbital» electronegativity and density functional theory A method for determination of «inductive» electronegativities is suggested. This provides tor correct theoretical calculation of a substituent electronegativities based on electronegativities of individual atoms and a substituent spatial structure. It is shown that the approach developed posses a number of important advantages, e.g. allows for the calculation of group electronegativity of isomeric substituents avoiding utilisation of an electronegativity equalisation principle. A utilisation of literature data summary and the method proposed by us allows to formulate a view on electronegativity as invariable fundamental immanent characteristic of a chemical element

"Inductive" Electronegativities of Substituents at Various Reaction Centers

A new method, based on the previously developed model of the inductive effect and on fundamental physical and geometric parameters of atoms and groups, is proposed for calculating the atomic and group electronegativities. This approach allowed refinement of a number of very important theoretical concepts, such as the nature of the group electronegativity and its correlation with the main quantitative characteristics of the substituent, the inductive and steric constants

The concept of electronegativity. the current state of the problem

A systematic account is given of the current ideas about atomic and group electronegativities and the trends in the development of the concept of electroncgativity are analysed. Attention is concentrated on the latest approaches to the definition of electronegativity - the concept of 'orbital' electronegativities and the density functional theory. A procedure is proposed for the determination of 'inductive' electronegativities, which permits a correct theoretical calculation of the electronegativity of a substituent from the electronegativities of individual atoms and the steric structure. It is shown that the approach developed has a series of important advantages - for example, it makes it possible to calculate the group electronegativities of isomeric substituents avoiding the principle of the equalisation of electronegativities. A survey of literature data and generalisation of the method proposed by the authors have made it possible to formulate the concept of electronegativity as an unchanging fundamental immanent characteristic of a chemical element. © 1998 Russian Academy of Sciences and Turpion Ltd

Electronegativity in the Density Functional Theory. Determination of the Electron Chemical Potential of the Ground State of a System in the Local Density Approximation

An iterative algorithm for simultaneous determination of the ground-state electron chemical potential and electron density of a multielectron system is formulated in terms of the density functional theory. With the energy potential in the local density approximation as an example it is shown that the equality of the electronegativities of the natural orbitals corresponds to the nonphysical electron density

A New Model of Inductive Effect: "Inductive" Group Electronegativities

A theoretical method is proposed for the calculation of group electronegativities of substituents based on the earlier elaborated new model of inductive effect. This approach makes it possible to calculate χ values on the basis of fundamental geometric and physical parameters of the atoms constituing a substituent, employing a simple and available mathematical procedure

Detailed EPR study of spin crossover dendrimeric iron(III) complex

The unusual magnetic behavior of the first dendritic Fe3+ complex with general formula [Fe(L)2]+Cl -·H2O based on a branched Schiff base has been investigated by electron paramagnetic resonance (EPR) and Mössbauer spectroscopy. EPR displays that complex consists of the three types of magnetically active iron centers: one S = 1/2 low-spin (LS) and two S = 5/2 high-spin (HS) centers with strong low-symmetry and weak distorted octahedral crystal fields. Analysis of the magnetic behavior reflected by I versus T (where I is the EPR lines integrated intensity of the spectrum) demonstrates that the dendritic Fe3+ complex has sufficiently different behavior in three temperature intervals. The first (4.2-50 K) interval corresponds to the antiferromagnetic exchange interactions between LS-LS, LS-HS, and HS-HS centers. The appearance of a presumable magnetoelectric effect is registered in the second (50-200 K) temperature interval, whereas a spin transition process between LS and HS centers occurs in the third (200-330 K) one. The coexistence of the magnetic ordering, presumable magnetoelectric effect, and spin crossover in one and the same material has been detected for the first time. The Mössbauer spectroscopy data completely confirm the EPR results. © 2013 American Chemical Society

Electronegativity in quantum chemistry

The possibility is discussed for determination of chemical potential (electronegativity) of an electron-nucleus system in terms of the quantum-mechanical density functional theory (DFT). The principle of complete leveling of chemical potentials of natural orbitals, formulated in the framework of DFT, cannot be regarded now as justified. The calculation of electronic chemical potential via difference schemes still remains the only procedure suitable for estimation of this quantity by quantum-chemical methods

Electronic chemical potential and orbital electronegativity of univalent substituents

The relations were analyzed between the electronic chemical potential of a chemical group in the ground state and the orbital chemical potential of its valence state, the latter being equal in absolute value to its orbital electronegativity. These quantities should be equivalent for univalent substituents whose ground electronic state can be described by one-determinant wave function allowing localization of molecular orbitals in a closed shell. In this case, the orbital electronegativity of a chemical group can be calculated in terms of nonempirical quantum-chemical methods. The results of the variation calculation of orbital electronegativities of a series of univalent substituents gave rise to a quantum-chemical scale of group electronegativities which may be used for testing of approximate calculation procedures

High-spin Fe(III) Schiff based complexes with photoactive ligands. Synthesis, EPR study and magnetic properties

© 2018 Elsevier Ltd A series of three novel Fe(III) compounds of the formula [FeL2]X (where X = Cl− (1), PF6− (2), NO3– (3), and L is a photoactive ligand, (4)-4-(((2-(ethylamino)ethyl)imino)methyl)-3-hydroxyphenyl 4-bromobenzoate) was synthesized and studied by means of electron paramagnetic resonance (EPR) and pulsed laser irradiation. The Fe3+ ions in these compounds are in a high-spin state. A thorough analysis of the EPR data suggests that compounds 1 and 2 undergo an order–disorder ferroelectric phase transition, and below the phase transition temperature (Tc = 100 and 200 K for compounds 1 and 2, respectively) a nonzero average electric dipole moment appears. To get an insight into molecular structure of Fe3+ ions and their supramolecular organization in low-temperature (LT) and high-temperature (HT) phases of compounds 1 and 2, a series of density functional theory calculations was performed. On the basis of our findings, the LT- and HT-phase structures were proposed for these compounds. It was also shown that, whereas the chloride and hexafluorophosphate anions are able to form a network of hydrogen bonds between the [FeL2]X units (ionic pairs), which enable an electric dipole ordering in the sample, the nitrate anions, in contrast, tend to form hydrogen bonds inside the ionic pair. This conclusion is evidenced by the observed EPR spectra, which are different for compound 3 and are not indicative of the existence of an order–disorder ferroelectric phase transition. The EPR data obtained upon irradiation of compound 1 show that photoexcitation in the UV region at 5 K destroys hydrogen bonds and converts cationic complexes into ligand-to-metal charge transfer (LMCT) states, in which the iron is ferrous, and the unpaired electron is located on the salicylidene moieties. The LMCT states decay back to the ferric one, and ferric complexes further form the most stable (LT) phase structure