Ab Initio Study of the Electronic Properties of a Silicene Anode Subjected to Transmutation Doping

In the present work, the electronic properties of doped silicene located on graphite and nickel substrates were investigated by first-principles calculations method. The results of this modeling indicate that the use of silicene as an anode material instead of bulk silicon significantly improves the characteristics of the electrode, increasing its resistance to cycling and significantly reducing the volume expansion during lithiation. Doping of silicene with phosphorus, in most cases, increases the electrical conductivity of the anode active material, creating conditions for increasing the rate of battery charging. In addition, moderate doping with phosphorus increases the strength of silicene. The behavior of the electronic properties of doped one- and two-layer silicene on a graphite substrate was studied depending on its number and arrangement of phosphorus atoms. The influence of the degree of doping with silicene/Ni heterostructure on its band gap was investigated. We considered the single adsorption of Li, Na, K, and Mg atoms and the polyatomic adsorption of lithium on free-standing silicene. © 2023 by the authors.122020100205-5, FUME-2022-0005; Ministry of Education and Science of the Russian Federation, MinobrnaukaThis work was executed in the frame of the scientific theme of Institute of High-Temperature Electrochemistry UB RAS, number FUME-2022-0005, registration number 122020100205-5 and supported by the Ministry of Education and Science of the Russian Federation

Integrated effect of atmosphere pollution and cutting on seed production of dandelion (Taraxacum officinale Wigg.) urban populations

© 2016, International Journal of Pharmacy and Technology. All rights reserved.We considered the influence of air pollution by road transport on the total number of seeds, seed weight and the formation of seeds able to germinate in the inflorescences of Taraxacum officinale Wigg cut off on the fourth day after flowering, and in the inflorescences formed on the parent plant. The monotonous dependence dose-response is characteristic for the seeds developed on the parent plant. The dependencies of other seed production indicators from air pollution intensity by motor traffic are nonmonotonic ones, which can be attributed to the paradoxical effects that appear brighter in the inflorescences cut off on the fourth day after flowering. The intensity of seed germination, formed on the mother plant, is also difficult and depends nonmonotonically on the degree of atmosphere contamination, but the seeds with the weight less than 0.25 mg are not developed. A significant influence on the relationship between the weight of seeds and their germination is made by negative impact factor duration. At the same weight (0,39 ± 0,02 mg) the maximum germination of the option “cut off florets” and a minimum one for the version “ripened on parent plant”. At the same time a lot of seeds correlated with their germination differently. For the seeds ripened in the cut off inflorescences R2 = 0.80 (p = 0.00027), and for the seeds ripened on the parent plant R2 = 0.55 (p = 0.008). The critical mass of viable seeds for their germination in cut off inflorescences made 0.23 ± 0.007 mg, which is 10% more than a certain critical mass of Taraxacum officinale seeds stated earlier

Surface Analysis of OFE-Copper X-Band Accelerating Structures and Possible Correlation to RF Breakdown Events

X-band accelerator structures meeting the Next Linear Collider (NLC) design requirements have been found to suffer vacuum surface damage caused by radio frequency (RF) breakdown, when processed to high electric-field gradients. Improved understanding of these breakdown events is desirable for the development of structure designs, fabrication procedures, and processing techniques that minimize structure damage. RF reflected wave analysis and acoustic sensor pickup have provided breakdowns localization in RF structures. Particle contaminations found following clean autopsy of four RF-processed travelling wave structures, have been catalogued and analyzed. Their influence on RF breakdown, as well as that of several other material-based properties, will be discussed.Comment: 21 pages, 8 figures, 4 tables, Submitted to JVST A as a proceeding of the 50th AVS conference (Baltimore, MD, 2-7 Nov 2003

The Bell Theorem as a Special Case of a Theorem of Bass

The theorem of Bell states that certain results of quantum mechanics violate inequalities that are valid for objective local random variables. We show that the inequalities of Bell are special cases of theorems found ten years earlier by Bass and stated in full generality by Vorob'ev. This fact implies precise necessary and sufficient mathematical conditions for the validity of the Bell inequalities. We show that these precise conditions differ significantly from the definition of objective local variable spaces and as an application that the Bell inequalities may be violated even for objective local random variables.Comment: 15 pages, 2 figure

Spin orientation of a two-dimensional electron gas by a high-frequency electric field

Coupling of spin states and space motion of conduction electrons due to spin-orbit interaction opens up possibilities for manipulation of the electron spins by electrical means. It is shown here that spin orientation of a two-dimensional electron gas can be achieved by excitation of the carriers with a linearly polarized high-frequency electric field. In (001)-grown quantum well structures excitation with in-plane ac electric field induces orientation of the electron spins along the quantum well normal, with the spin sign and the magnitude depending on the field polarization.Comment: 5 pages, 1 figur

Electric-field switchable magnetization via the Dzyaloshinskii-Moriya interaction: FeTiO_3 versus BiFeO_3

In this article we review and discuss a mechanism for coupling between electric polarization and magnetization that can ultimately lead to electric-field switchable magnetization. The basic idea is that a ferroelectric distortion in an antiferromagnetic material can "switch on" the Dzyaloshinskii-Moriya interaction which leads to a canting of the antiferromagnetic sublattice magnetizations, and thus to a net magnetization. This magnetization M is coupled to the polarization P via a trilinear free energy contribution of the form P(M x L), where L is the antiferromagnetic order parameter. In particular, we discuss why such an invariant is present in R3c FeTiO_3 but not in the isostructural multiferroic BiFeO_3. Finally, we construct symmetry groups that in general allow for this kind of ferroelectrically-induced weak ferromagnetism.Comment: 15 pages, 3 images, to appear in J. Phys: Condens. Matter Focus Issue on Multiferroic

Origin of magnetoelectric behavior in BiFeO3_3

The magnetoelectric behavior of BiFeO$_3$ has been explored on the basis of accurate density functional calculations. The structural, electronic, magnetic, and ferroelectric properties of BiFeO$_3$ are predicted correctly without including strong correlation effect in the calculation. Moreover, the experimentally-observed elongation of cubic perovskite-like lattice along the [111] direction is correctly reproduced. At high pressure we predicted a pressure-induced structural transition and the total energy calculations at expanded lattice show two lower energy ferroelectric phases, closer in energy to the ground state phase. Band-structure calculations show that BiFeO$_3$ will be an insulator in A- and G-type antiferromagnetic phases and a metal in other magnetic configurations. Chemical bonding in BiFeO$_3$ has been analyzed using various tools and electron localization function analysis shows that stereochemically active lone-pair electrons at the Bi sites are responsible for displacements of the Bi atoms from the centro-symmetric to the noncentrosymmetric structure and hence the ferroelectricity. A large ferroelectric polarization (88.7 $\mu$C/cm$^{2}$) is predicted in accordance with recent experimental findings. The net polarization is found to mainly ($>$ 98%) originate from Bi atoms. Moreover the large scatter in experimentally reported polarization values is due to the large anisotropy in the spontaneous polarization.Comment: 19 pages, 12 figures, 4 table

On the nature of steady states of spin distributions in the presence of spin-orbit interactions

In the presence of spin-orbit interactions, the steady state established for spin distributions in an electric field is qualitatively different from the steady state for charge distributions. This is primarily because the steady state established for spin distributions involves spin precession due to spin-orbit coupling. We demonstrate in this work that the spin density matrix in an external electric field acquires two corrections with different dependencies on the characteristic momentum scattering time. One part is associated with conserved spins, diverges in the clean limit and is responsible for the establishment of a steady-state spin density in electric fields. Another part is associated with precessing spins, is finite in the clean limit and is responsible for the establishment of spin currents in electric fields. Scattering between these distributions has important consequences for spin dynamics and spin-related effects in general, and explains some recent puzzling observations, which are captured by our unified theory.Comment: 10 pages, 1 figur

DFT-based calculations of silicon complex structures in KF–KCl–K2SiF6 and KF–KCl–K2SiF6–SiO2 melts

The length and energy of bonds in the complex anions of silicon formed in KF−KCl−K2SiF6 and KF−KCl−K2SiF6–SiO2 melts were evaluated using the method of first-principles molecular dynamics, accomplished by means of the Siesta program. The effect of K+ (from the second coordination sphere) on the stability of these complexes was studied. The bond lengths in the silicon complexes was found to change with increasing amount of the potassium ions. It was established that the following complexes [SiO4]4-, [SiO3F]3- and [SiF6]2- are the most stable in KF−KCl−K2SiF6 and KF−KCl––K2SiF6–SiO2 melts. The [SiO4]4- and [SiF6]2- complexes are thermally stable in the molten salt in the temperature range of 923–1073 K, whereas the [SiF7]3-structure, which is typical for the lattice of crystalline K3SiF7, is unstable in this temperature range. In the KF−KCl−K2SiF6−SiO2 melts, conditions above 1043 K were created allowing the transformation of [SiО3F]3- into [SiO4]4-. Within the studied temperature mode, the Si–F bond length is in the range 1.5––1.9 Å and the Si–O bond lengths is 1.5–1.7 Å. The obtained results are in a good agreement with in situ data of Raman spectroscopy for the KF−KCl−K2SiF6 and KF–KCl–K2SiF6–SiO2 melts. © 2019 Serbian Chemical Society. All rights reserved.Russian Science Foundation, RSF: 18-73-00227The work was accomplished with the financial support of the Russian Science Foundation, Project No. 18-73-00227