Electronic structure and stability of nonstoichiometric titanium monoxide TiOy with structural vacancies in one of the sublattices

The electronic structure of nonstoichiometric titanium monoxide TiOy with different compositions y, which contains structural vacancies either in the metallic sublattice or in the nonmetallic sublattice, has been investigated using the supercell method within the DFT-GGA approximation with pseudopotentials. The cases of ordered and disordered arrangements of vacancies have been considered. It has been found that the complete removal of vacancies from the sublattice is energetically unfavorable, and the ordering of oxygen vacancies according to the type of the Ti6O5□1 superstructure, as well as titanium vacancies according to the Ti5black small square1O6 type, does not lead to the stabilization of the B1 basic structure of titanium monoxide. © 2013 Pleiades Publishing, Ltd

Structural disorder and short-range order in full Heusler alloys Fe2VAl and Co2CrAl from first principles calculations

Heusler alloys are intensively studied and applied in various spintronic devices. First principles calculations of their electronic structure allow to predict promising compounds with high spin polarization. However the theoretical predictions usually substantially deviate from experimental data. One of the reason is incorrect structural models used in the calculations. Heusler alloys are apt to form various disordered modifications with high concentration of antisite defects. In this paper we considered the effects of structural order and disorder on the electronic structure, stability and magnetic properties of full Heusler alloys Fe2VAl and Co2CrAl. The ordered Fe2VAl is non-magnetic narrow-gap semiconductor, the ordered Co2CrAl is a ferromagnet with metal behavior for majority spin band and narrow-gap semiconductor for minority one. When disordering Fe2VAl becomes a ferromagnetic metal. Co2CrAl loses minority band gap and its spontaneous magnetization reduces by 32%. Introduction of short range order in the disordered structure by increasing the portion of clusters specific for bcc structure further raised the magnetization in Fe2VAl and did not change it in Co2CrAl. © 2019 Elsevier B.V.Russian Foundation for Basic Research, RFBR: 16-52-48012This work was supported by the project of the Russian Foundation for Basic Research No. 16-52-48012 , the state assignment of Minobrnauki of Russia (theme “Electron” No. АААА-А18-118020190098-5 ). The calculations were performed using “Uran” supercomputer of IMM UB RAS. The authors thank E. I. Shreder and E. D. Baglasov for help with the review of experimental results

Internal energy and parameters of the order-disorder phase transition in titanium monoxide TiO y

Quantum-mechanical ab initio calculations are used to simulate the free energy functions for titanium monoxide TiO y . The effect of the long-range order of the Ti5O5 type superstructure on the internal energy of the compound is studied by the supercell method. The dependences of the configuration entropy and free energy on the long-range order parameter are determined. It is found that the order-disorder phase transition in titanium monoxide must occur in accordance with the mechanism of the first-order phase transition with a critical value of the long-range order parameter of 0.971. The calculated parameters of the phase transition are compared with the experimental data and the results obtained using the model of point charges and by calculating the Madelung energy. It is concluded that the short-range order and the phonon entropy must be taken into account in calculating the equilibrium phase diagrams for strongly nonstoichiometric compounds. © 2013 Pleiades Publishing, Ltd

Simulation of the short-range order in disordered cubic titanium monoxide TiO1.0

A model of the atomic structure with the short-range order in the vacancy distribution for the disordered cubic phase of titanium monoxide TiO1.0 has been proposed. The effect of the short-range order on the electronic structure and the stability of the compound has been studied by the supercell method within the DFT-GGA approximation with the use of pseudopotentials. It has been established that the appearance of the short-range order considerably decreases the total energy. The decrease in the energy is comparable with the energy gain during the ordering of the vacancies according to the type of monoclinic superstructure Ti5O5 to the long-range order parameter η = 0.7. It has been shown that the discrepancies between the theoretical and experimental electronic spectra of titanium monoxide can be explained by allowance for the short range order. © 2013 Pleiades Publishing, Ltd

Vacancies in ordered and disordered titanium monoxide: Mechanism of B1 structure stabilization

The electronic structure and stability of three phases of titanium monoxide TiOy with B1 type of the basic structure have been studied. Cubic phase without structural vacancies, TiO, and two phases with structural vacancies, monoclinic Ti5O5 and cubic disordered TiO 1.0, was treated by means of first-principles calculations within the density functional theory with pseudo-potential approach based on the plane wave's basis. The ordered monoclinic phase Ti5O5 was found to be the most stable and the cubic TiO without vacancies the less stable one. The role of structural vacancies in the titanium sublattice is to decrease the Fermi energy, the role of vacancies in the oxygen sublattice is to contribute to the appearance of Ti-Ti bonding interactions through these vacancies and to reinforce the Ti-Ti interactions close to them. Listed effects are significantly pronounced if the vacancies in the titanium and oxygen sublattices are associated in the so called "vacancy channels" which determine the formation of vacancy ordered structure of monoclinic Ti5O 5-type. © 2013 Elsevier Inc

Internet Commerce As a Possible Direction for the Development of Entrepreneurship Supply Chain and Information Management

Information and communications technology in supply chain management has enabled corporations to use offshore facilities for outsourcing commercial activities. One of the current trends in the global economic space is the formation of an information economy that allows fulfilling the requirements for the interaction organization between business entities at a high organizational level. At the same time, the traditional economy is significantly lagging behind in the development of new economic trends such as digitalization, supply chain and information management, which necessitates to create effective measures aimed at developing the economic information space: in particular, the Internet entrepreneurship supply chain management. To solve this problem, it is proposed to use a combination of quantitative and qualitative methods, including test analysis method, logical-structural and causal analysis, as well as synthesis of literature, strategic analysis method, content analysis, applied economic and statistical methods, and sociological survey. Using these methods allowed determining the set of factors affecting the growth and development of the Internet entrepreneurship supply chain. We classified e-commerce models according to various criteria, formed different directions of the impact of government regulation on the e-commerce market and information management in the supply chain system. The identification of factors holding back the development of e-commerce made it possible to determine the nature of their negative impact on the development of the Internet entrepreneurship supply chain and to give some recommendations on improving the efficiency of state regulation of this sphere and ensuring its greater attractiveness in the minds of consumers. Application of the obtained results will make it possible to prepare regulatory and program documents in the field of state regulation of the Internet entrepreneurship supply chain and determine possible directions for its development in the future

Entorno educativo digital como herramienta de cambios complejos de la actividad pedagógica del profesor

The authors of the article identified four basic functions of the use of information technology in the course of training future representatives of a profession: information and training, forming, evaluation and correction, research.  It is noted that these functions do not operate separately, but as elements of a single system, depending on the conditions determined by the features of the information EE. The analysis allows the authors of the article to assert that at this stage of the educational process evolution the main task is to create a methodology related to the use of information management technologies in the development of electronic materials of educational nature and their implementation in the context of pedagogical activity.Los autores del artículo identificaron cuatro funciones básicas del uso de la tecnología de la información en el curso de la capacitación de futuros representantes de una profesión: información y capacitación, formación, evaluación y corrección, investigación. Cabe señalar que estas funciones no funcionan por separado, sino como elementos de un solo sistema, dependiendo de las condiciones determinadas por las características de la información EE. El análisis permite a los autores del artículo afirmar que en esta etapa de la evolución del proceso educativo, la tarea principal es crear una metodología relacionada con el uso de tecnologías de gestión de la información en el desarrollo de materiales electrónicos de naturaleza educativa y su implementación en el contexto de actividad pedagógica

Kinetics of internal structures growth in magnetic suspensions

The kinetics of aggregation of non Brownian magnetizable particles in the presence of a magnetic field is studied both theoretically and by means of computer simulations. A theoretical approach is based on a system of Smoluchowski equations for the distribution function of the number of particles in linear chain-like aggregates. Results obtained in the two dimensional (2D) and three dimensional (3D) models are analyzed in relation with the size of the cell, containing the particles, and the particle volume fraction φ. The theoretical model reproduces the change of the aggregation kinetics with the size of the cell and with the particle volume fraction as long as the lateral aggregation of chains is negligible. The simulations show that lateral aggregation takes place when, roughly, φ2D>5% and φ3D>1.5%. Dependence of the average size of the chains with time can be described by a power law; the corresponding exponent decreases with the particle volume fraction in relation with the lateral aggregation. In the 3D simulations, dense labyrinthine-like structures, aligned along the applied field, are observed when the particle concentration is high enough (φ3D>5%). © 2012 Elsevier B.V. All rights reserved

Role of structural vacancies in the stabilization of the basic B1 structure in nonstoichiometric titanium monoxide TiO y

The electron structures and formation enthalpies of vacancy-free cubic TiO, vacancy-ordered monoclinic Ti5O5, and vacancy-disordered cubic TiO y have been investigated using DFT+GGA calculations. Ti5O5 was found to be the stablest phase and TiO was found to be the least stable. The reason for the stability of the titanium and oxygen vacancies in the basic B1 structures of Ti5O5 and TiO y has been deduced. The titanium vacancies lead to a decrease in the Fermi energy. Oxygen vacancies cause strengthening in covalent Ti-Ti bonding. © 2013 Allerton Press, Inc