Electronic correlations and crystal structure distortions in BaBiO3

BaBiO3 is a material where formally Bi4+ ions with the half-filled 6s-states form the alternating set of Bi3+ and Bi5+ ions resulting in a charge ordered insulator. The charge ordering is accompanied by the breathing distortion of the BiO6 octahedra (extension and contraction of the Bi-O bond lengths). Standard Density Functional Theory (DFT) calculations fail to obtain the crystal structure instability caused by the pure breathing distortions. Combining effects of the breathing distortions and tilting of the BiO6 octahedra allows DFT to reproduce qualitatively experimentally observed insulator with monoclinic crystal structure but gives strongly underestimate breathing distortion parameter and energy gap values. In the present work we reexamine the BaBiO3 problem within the GGA+U method using a Wannier functions basis set for the Bi 6s-band. Due to high oxidation state of bismuth in this material the Bi 6s-symmetry Wannier function is predominantly extended spatially on surrounding oxygen ions and hence differs strongly from a pure atomic 6s-orbital. That is in sharp contrast to transition metal oxides (with exclusion of high oxidation state compounds) where the major part a of d-band Wannier function is concentrated on metal ion and a pure atomic d-orbital can serve as a good approximation. The GGA+U calculation results agree well with experimental data, in particular with experimental crystal structure parameters and energy gap values. Moreover, the GGA+U method allows one to reproduce the crystal structure instability due to the pure breathing distortions without octahedra tilting

Methodology of design of the thin steel strip cold rolling energy efficient technology

The article states basic principles of the methodology of design of the thin steel strip production energy efficient technology, according to which the design process is structurally divided into seven interrelated modules of certain functions. Implementation of the represented approach resulted in the efficient technical mode of rolling providing reduction of overall power consumption subject to compliance with the requirements to quality parameters of the strip

Condensation of Silica Nanoparticles on a Phospholipid Membrane

The structure of the transient layer at the interface between air and the aqueous solution of silica nanoparticles with the size distribution of particles that has been determined from small-angle scattering has been studied by the X-ray reflectometry method. The reconstructed depth profile of the polarizability of the substance indicates the presence of a structure consisting of several layers of nanoparticles with the thickness that is more than twice as large as the thickness of the previously described structure. The adsorption of 1,2-distearoyl-sn-glycero-3-phosphocholine molecules at the hydrosol/air interface is accompanied by the condensation of anion silica nanoparticles at the interface. This phenomenon can be qualitatively explained by the formation of the positive surface potential due to the penetration and accumulation of Na+ cations in the phospholipid membrane.Comment: 7 pages, 5 figure

Sustainable Energy for Smart City

The article presents the results of a study of structural changes in the energy sector serving digital technologies for the urban environment of the future that is being created now. The study considers country-specific factors and problems of ensuring the sustainability of heat and power supply. The authors look at the priority areas of a new phase of electrification aimed at the development of advanced energy-saving smart technologies, electric transport, electric cars and appropriate energy and utility infrastructure. The case is studied of developing engineering, technical, organizational and economic solutions when overhauling the heat supply system in a ‘smart’ residential district of Yekaterinburg, one of Russia’s megalopolises, that is being designed and constructed on the basis of the principles of intelligent engineering infrastructure.The work was supported by Act 211 of the Government of the Russian Federation, contract 02.A03.21.0006

Gauge vortex dynamics at finite mass of bosonic fields

The simple derivation of the string equation of motion adopted in the nonrelativistic case is presented, paying the special attention to the effects of finite masses of bosonic fields of an Abelian Higgs model. The role of the finite mass effects in the evaluation of various topological characteristics of the closed strings is discussed. The rate of the dissipationless helicity change is calculated. It is demonstrated how the conservation of the sum of the twisting and writhing numbers of the string is recovered despite the changing helicity.Comment: considerably revised to include errata to journal versio