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Vol 59, No 6 (2017)

Metals

Ionization potential of a metal cluster containing vacancies

Pogosov V.V., Reva V.I.

Abstract

A consistent procedure for determining the ionization potential of a large metal cluster of radius RN, v, consisting of N atoms and Nv vacancies, is proposed. The perturbation theory in small parameters Rv/RN, v and Lv/Rv (Rv and Lv are average distance between vacancies and the length of electron scattering on vacancies, respectively) is constructed in the effective-medium approximation for the electron ground state energy. The effective vacancy potential profile, the electron scattering phase and length are calculated by the Kohn–Sham method for a macroscopic metal in the stable jelly model. The obtained analytical dependences can be useful to analyze the results of photoionization experiments and to determine the size dependence of the vacancy concentration, including that near the melting temperature.

Physics of the Solid State. 2017;59(6):1063-1070
pages 1063-1070 views

Method for determining the electron and positron work function from a metal containing vacancies

Pogosov V.V.

Abstract

A method is proposed that combines self-consistent solutions for a monovacancy in metal without regard to the outer surface and the solution in the stable jelly model for metal with homogeneous volume and flat surface, but a lowered vacancy density due to the presence of a superlattice of vacancy voids with relative concentration cv. When using cv as a small parameter, all energy characteristics are expanded in a functional series. Zero expansion terms relate to defect-free metal, and linear in cv corrections are expressed in terms of its characteristics. Exact formulas allowing the consideration of the effect of vacancies on the electron and positron work function are derived. Characteristics are calculated at various temperatures for Al and Na by the Kohn–Sham method. The method application to spherical clusters is briefly discussed.

Physics of the Solid State. 2017;59(6):1071-1075
pages 1071-1075 views

Semiconductors

Electron transfer in the structure of a photorefractive doped Bi12TiO20: Ru crystal

Avanesyan V.T., Paima K.I., Stozharov V.M.

Abstract

The ac conductivity of Bi12TiO20: Ru crystals has been studied in the frequency range 102–106 Hz and at temperatures 293–773 K. The experimental data have been analyzed in the framework of the model of correlated barrier hops. In this material, the potential barriers are due to the existence of a block structure, crystal lattice defects, and also the presence of a ruthenium impurity. The microparameters characterizing the charge transfer in doped bismuth titanate single crystals have been determined.

Physics of the Solid State. 2017;59(6):1076-1079
pages 1076-1079 views

Electrical conductivity in single crystals of GaSexTe1 – x solid solutions in strong electrical fields

Tagiev B.G., Tagiev O.B.

Abstract

This paper presents some results of studying the Poole–Frenkel effect with allowance for shielding in layered GaSe and GaTe single crystals and their solid solutions in strong electrical fields of up to 105 V/cm at temperatures of 103–250 K. According to the relationship \(\left(\frac{\sigma}{\sigma(0)}\right)^{1/2}\) log\(\frac{\sigma}{\sigma(0)} = E\sqrt{\frac{\varepsilon}{4\pi n(0)kT}}\), there exists a linear dependence between \(\left(\frac{\sigma}{\sigma(0)}\right)^{1/2}\) log\(\frac{\sigma}{\sigma(0)}\) and the electrical field E (σ is the electrical conductivity in strong electrical fields, and σ(0) is the electrical conductivity in the ohmic region). The slopes of these lines have been determined at different temperatures (103–250 K) by estimating the concentration of current carriers n(0) = 3 × 1013–5 × 1015 cm–3 in the ohmic region of the electrical conductivity of solid solutions of layered GaSexTe1–x single crystals (x = 1.00, 0.95, 0.90, 0.80, 0.70, 0.30, 0.20, 0.10, 0).

Physics of the Solid State. 2017;59(6):1080-1084
pages 1080-1084 views

State equations and properties of various polymorphous modifications of silicon and germanium

Magomedov M.N.

Abstract

The state equations and the pressure dependences of the lattice properties have been obtained for various polymorphous modifications of silicon and germanium using the Mie–Lennard-Jones pair interatomic potential and the Einstein crystal model. It is shown that the elastic-type interatomic potential gives the best results for the semiconductor phase and the plastic-type interatomic potential for the metalized phases whose potential well depth is significantly smaller. The pressure dependences of the lattice properties are calculated along isotherm 300 K and the jumps of the properties during the phase transition from the diamond structure to the β-Sn phase are evaluated for both silicon and germanium. The calculated results agree well with the experimental data.

Physics of the Solid State. 2017;59(6):1085-1093
pages 1085-1093 views

Electrodynamic response of Ca1 – xPbxTiO3 two-phase solid solution in a wide frequency range

Komandin G.A., Porodinkov O.E., Spektor I.E., Iskhakova L.D., Bush A.A., Kamentsev K.E., Seregin D.S.

Abstract

The dielectric response of Ca1–xPbxTiO3 two-phase ceramics is studied in a wide frequency range, from 120 Hz to 100 THz, using impedancemetric radio-frequency methods and infrared spectroscopy. The problems of applications of various dispersion models to analyze infrared spectra of disordered ceramics in which high permittivities are formed in the microwave–terahertz ranges are discussed. The effect of low-frequency relaxation processes on the infrared spectrum and the formation of the constant level of dielectric losses is indicated.

Physics of the Solid State. 2017;59(6):1094-1102
pages 1094-1102 views

Magnetism

A study of the critical properties of the Ising model on body-centered cubic lattice taking into account the interaction of next behind nearest neighbors

Murtazaev A.K., Ramazanov M.K., Kurbanova D.R., Badiev M.K., Abuev Y.K.

Abstract

The replica Monte Carlo method has been used to investigate the critical behavior of a threedimensional antiferromagnetic Ising model on a body-centered cubic lattice, taking into account interactions of the adjacent behind neighbors. Investigations are carried out for the ratios of the values of exchange interactions behind the nearest and next nearest neighbors k = J2/J1 in the range of k ∈ [0.0, 1.0] with the step Δk = 0.1. In the framework of the theory of finite-dimensional scaling the static critical indices of heat capacity α, susceptibility γ, of the order parameter β, correlation radius ν, and also the Fisher index η are calculated. It is shown that the universality class of the critical behavior of this model is kept in the interval of k ∈ [0.0, 0.6]. It is established that a nonuniversal critical behavior is observed in the range k ∈ [0.8, 1.0].

Physics of the Solid State. 2017;59(6):1103-1109
pages 1103-1109 views

The peculiarities of behavior of nuclei remagnetization in a magnetic field in uniaxial films

Vakhitov R.M., Solonetskii R.V., Larionov I.B.

Abstract

The influence of magnetic field on the structure and properties of magnetic inhomogeneities generated in the defects of the type of “potential well” in magnetic uniaxial films has been theoretically investigated. It is shown that the behavior of high-amplitude and low-amplitude inhomogeneities in the magnetic field varies considerably, and the causes of such differences are identified. It is established that in some cases, when these inhomogeneities do not exist in the absence of a field, they can be induced in a nonzero field. Possibilities to identify both types of heterogeneities at their experimental detection are considered.

Physics of the Solid State. 2017;59(6):1110-1117
pages 1110-1117 views

Ferroelectricity

Electrocaloric effect in triglycine sulfate under equilibrium and nonequilibrium thermodynamic conditions

Bondarev V.S., Mikhaleva E.A., Flerov I.N., Gorev M.V.

Abstract

The direct and indirect measurements of intensive electrocaloric effect in a triglycine sulfate ferroelectric crystal are performed under equilibrium and nonequilibrium thermodynamic conditions implemented in the adiabatic calorimeter. The effect of the electric field parameters (frequency, profile, and strength) on the value of the effect and degree of its reversibility are studied. The difference between the temperature variation values in a switched-on and switched-off dc field under quasi-isothermal conditions is established. The low-frequency periodic electric field induces the temperature gradient along the electrocaloric element and heat flux from its free end to the thermostated base. A significant excess of the field switching-off rate over the switching-on rate leads to a noticeable intensification of the cooling effect.

Physics of the Solid State. 2017;59(6):1118-1126
pages 1118-1126 views

Mechanical Properties, Physics of Strength, and Plasticity

The effect of small-amplitude load oscillations on the nanocontact characteristics of materials in nanoindentation

Golovin Y.I., Korenkov V.V., Razlivalova S.S.

Abstract

A continuous stiffness measurement method allowing one to obtain physical-mechamical characteristics of materials in the process of indentation during gradually increasing loading has been scrutinized. The limits of applicability of this approach depend on the testing conditions at which the additional smallamplitude oscillations exert no influence on the mechanics, kinetics, and plastic strain of material being in contact with the indenter. As is shown by taking as examples specimens with amorphous structure, and fcc and bcc lattices, various techniques for determining the nanocontact characteristics of materials are different by their sensitivity to small-amplitude load oscillations. The oscillation amplitudes and the indentation depth ranges where one can neglect the oscillation effects have been evaluated. The impacts of the oscillations on the behavior of the contact (local) characteristics of the studied materials in supercritical modes have been established.

Physics of the Solid State. 2017;59(6):1127-1138
pages 1127-1138 views

Impurity Centers

Effect of oxygen impurity on the efficiency of the formation of complexes with H-bond and aggregation of color centers in lithium fluoride

Nebogin S.A., Bryukvina L.I., Ivanov N.A., Glazunov D.S.

Abstract

The effect of impurities on the efficiency of the formation of color centers and hydrogen-bonded molecular complexes upon exposure to various radiations in lithium fluoride crystals grown in air is studied. The results of experiments for measuring optical properties, IR vibrational spectra, luminescence, and thermally stimulated luminescence are presented. The fact that the band in the range of 1800–2300 cm–1 corresponds to stretching vibrations of a complex with strong hydrogen bond is proved based on the Fermi-resonance perturbation in the region of 2080 cm–1, shaped as the Evans hole and bands A, B, and C. It is shown that the composition of these complexes includes an OH ion and an HF molecule. The crucial role of O2‒Va+ oxygen dipoles in the aggregation efficiency and gradient distribution of color centers and radiation resistance of hydroxyl ions is revealed. It is shown that products of radiation decomposition of OH ions stimulate, while decay of O2‒Va+ dipoles suppress, the formation of positively charged color centers.

Physics of the Solid State. 2017;59(6):1139-1145
pages 1139-1145 views

Identification of paramagnetic nitrogen centers (P1) in diamond crystallites synthesized via the sintering of detonation nanodiamonds at high pressure and temperature

Efimov N.N., Minin V.V., Kidalov S.V., Vul’ A.Y., Osipov V.Y., Shakhov F.M.

Abstract

Diamond single crystals synthesized from powder detonation nanodiamonds (DNDs) by means of treatment at high pressures (P ~ 7 GPa) and temperatures (T > 1300°C) have been studied by electron paramagnetic resonance (EPR). A key feature of treatment (high-pressure high–temperature (HPHT) sintering) is the use of low molecular weight alcohols in the process. The appearance of a hyperfine EPR signal structure due to “paramagnetic nitrogen” (P1 centers) is explained by the growth of submicron and micron diamond single crystals from DND nanocrystals by the oriented attachment and coalescence mechanism. Such growth and coarsening of crystals appreciably decreases the concentration of paramagnetic centers, the presence of which hinders the detection of a hyperfine structure in the EPR signal from P1 centers, in the near-surface areas of coalesced and grown together DND particles. It has been shown that the concentration of paramagnetic defects of all types decreases to ~3.1 × 1018 g–1 (~60 ppm) during HPHT treatment at T = 1650°C. This causes the successful identification of P1 centers, whose fraction is no less than ~40% of the total amount of paramagnetic centers in microcrystals synthesized by HPHT sintering.

Physics of the Solid State. 2017;59(6):1146-1153
pages 1146-1153 views

Optical Properties

Effect of a Coulomb well in (In, Ga)As/GaAs quantum wells

Seisyan R.P., Kavokin A.V., Moumanis K., Sasin M.E.

Abstract

Magnetooptical investigation of exciton transitions in high-quality quantum wells of an (In, Ga)As/GaAs heterosystem has been carried out. Investigation of transmission of free-hanging samples detached from the substrate in the magnetic fields of up to 12 T revealed a rich fine structure associated with various heavy-hole and light-hole exciton transitions. In particular, transitions from the excited states of light holes localized in a Coulomb potential produced by an electron along the heterojunction axis (a Coulomb well) have been detected. Taking into account consistently stresses, formation of Landau levels, the binding energies of excitons (diamagnetic excitons), and the effect of a Coulomb well, we have succeeded to describe the experimental results with the use of a self-consistent variational procedure. As a result, new features in the structure of optical transitions have been explained and the effective masses of electrons and holes of excitons formed by both heavy and light holes have been determined with a high accuracy.

Physics of the Solid State. 2017;59(6):1154-1170
pages 1154-1170 views

Spectral and structural characteristics of Lu1 – xyCexTbyBO3 orthoborates prepared by the hydrothermal synthesis method

Shmurak S.Z., Kedrov V.V., Kiselev A.P., Fursova T.N., Rybchenko O.G.

Abstract

The structure, IR absorption spectra, morphology, and photoluminescence spectral characteristics of Lu1–xyCexTbyBO3 solid solutions prepared by the hydrothermal synthesis method have been investigated. According to the X-ray powder diffraction data, the Lu1–xyCexTbyBO3 samples hydrothermally synthesized at a temperature T = 200°C have the vaterite structure, and all the observed diffraction peaks correspond to the hexagonal phase with the space group P63/mmc, which is isostructural to pure lutetium borate LuBO3. Annealing of these samples at T = 970°C leads to a change in the structural modification and to the transition of the samples to the monoclinic phase with the space group C2/c. It has been found that, after annealing of these samples at temperatures T = 800–970°C, the luminescence intensity of Tb3+ ions upon excitation in the absorption band of Ce3+ ions increases by more than two orders of magnitude and becomes much higher than that in compounds of the same composition, but prepared by high-temperature synthesis. At the same time, annealing of lutetium borate doped only with terbium does not lead to a significant change in the luminescence intensity of Tb3+ ions. The possible reasons for a multiple increase in the luminescence intensity of terbium ions due to the annealing of the hydrothermally synthesized lutetium orthoborate samples doped with cerium and terbium ions have been discussed.

Physics of the Solid State. 2017;59(6):1171-1182
pages 1171-1182 views

Lattice Dynamics

Anomalous low-frequency phonons in ZrB12

Ponosov Y.S.

Abstract

The influence of pressure and temperature on low-frequency lines (100–300 cm–1) in Raman spectra of ZrB12 and LuB12 single crystals has been investigated. These spectral features have been identified as one-phonon and two-phonon excitations of the acoustic branches of the phonon spectrum. It has been found that the observed spectra of ZrB12 single crystals are more structured and indicate the development of phonon anomalies with a decrease in the temperature. Despite the fact that the low-frequency features in the phonon spectrum of ZrB12 are characterized by a high value of the isothermal Grüneisen parameter, their isobaric Grüneisen parameter has a negative value. This indicates large contributions from the fourth-order anharmonicity, which significantly exceed the volume effects. The appearance of narrow lines in the frequency range from 155 to 175 cm–1 at temperatures T < 100 K suggests the possibility of a structural transition with an incomplete softening of the lattice.

Physics of the Solid State. 2017;59(6):1183-1189
pages 1183-1189 views

Phase Transitions

Order–order transition structural state in titanium monoxide TiO1.0

Kostenko M.G., Sharf S.V., Rempel A.A.

Abstract

A new class of defect structures in which point defects of a crystal lattice simultaneously occupy sites of two different superstructures is proposed. The formation of these structural modifications is due to a second-order order–order phase transition that does not occur to the end. The allowable relation between the long-range order parameters in the structural modification formed by a combination of the monoclinic (M5X5)mon (space group C2/m (A2/m)) and the cubic (M5X5)cub (space group Pm3m) of the superstructures is studied using an atom–vacancy ordering in titanium monoxide TiO1.0. The thermodynamic calculations show that the proposed structural modification is equilibrium and must form instead of assumed high-temperature cubic phase (Ti5O5)cub.

Physics of the Solid State. 2017;59(6):1190-1195
pages 1190-1195 views

Formation of new structural states in compressed BaTiO3 nanopowders

Shmyt’ko I.M., Frolov D.D., Aronin A.S., Ganeeva G.R., Kedrov V.V.

Abstract

The structural changes in BaTiO3 nanocrystal powder and tablets have been probed via X-ray diffraction, scanning electron and transmission microscopy, and differential calorimetry after successive hightemperature annealing in air. It is shown that, beginning with the annealing temperature of 1200°C, significant amount of the Ba2TiO4 phase forms in the tablets together with the BaTiO3 phase. This phase is equilibrium one; it practically vanishes when the annealing temperature decreases to 700–600°C; and this phase practically restored to the initial state when the annealing temperature is again increased to 1200°C. Annealing the powders causes no formation of new phases, but an increase in their crystallite sizes. A probable reason of the emergence of Ba2TiO4 phase in tablets and its absence in free powder is discussed, as well.

Physics of the Solid State. 2017;59(6):1196-1205
pages 1196-1205 views

Low-Dimensional Systems

Chemical and phase compositions of multilayer nanoperiodic a-SiOx/ZrO2 structures subjected to high-temperature annealing

Boryakov A.V., Surodin S.I., Nikolichev D.E., Ershov A.V.

Abstract

The chemical and the phase compositions of multilayer nanoperiodic SiOx/ZrO2 structures prepared by vacuum evaporation from separated sources and subjected to high-temperature annealing have been studied by X-ray photoelectron spectroscopy with a layer-by-layer etching. It is found that, under deposition conditions used, the silicon suboxide layers had the stoichiometric coefficient x ~1.8 and the zirconium-containing layers were the stoichiometric zirconium dioxide. It was found, using X-ray photoelectron spectroscopy, that annealing of the multilayer structures at 1000°C leads to mutual diffusion of the components and chemical interaction between ZrO2 and SiOx with predominant formation of zirconium silicate at heteroboundaries of the structures. The SiOx layers of the annealed nanostructures contained ~5 at % elemental silicon as a result of the phase separation and the formation of fine silicon nanocrystals.

Physics of the Solid State. 2017;59(6):1206-1214
pages 1206-1214 views

Biexciton in II–VI quantum dots with different localization potentials

Golovatenko A.A., Semina M.A., Rodina A.V., Shubina T.V.

Abstract

We present a comparative study of the influence of the form of a localization potential on the binding energy of the biexciton in spherically symmetric quantum dots based on II–VI compounds. The proposed criterion for the comparison of potentials of different forms—the box potential, the harmonic oscillator, and the Gaussian potential—is based on the identical localization of charge carriers of the same sign in these potentials. Calculations of the biexciton binding energy have been performed using the variational method within the framework of the kp-perturbation theory taking into account additional polarization terms in the wave functions of the electron and hole subsystems, as well as the complex structure of the valence band. The obtained results have demonstrated that the presence of a smoothly varying finite-height potential in Cd(Zn)Se/ZnSe quantum dots can lead to a more efficient localization in the case of the biexciton in comparison with the exciton, which is of interest for the implementation of fast-acting quantum light emitters.

Physics of the Solid State. 2017;59(6):1215-1224
pages 1215-1224 views

Surface Physics and Thin Films

Electron microscopic investigation of the kinetics of the layer and island crystallization of amorphous V2O3 films deposited by pulsed laser evaporation

Bagmut A.G.

Abstract

An electron microscopic investigation was performed on the kinetics of the layer and island crystallization of amorphous V2O3 films deposited by pulsed laser evaporation of vanadium in an oxygen atmosphere. The crystallization was initiated by the action of an electron beam on an amorphous film in the column of a transmission electron microscope. The kinetic curves were plotted on the basis of a frame-by-frame analysis of the video recorded during the crystallization of the film. It was found that the layer crystallization of amorphous films is characterized by a quadratic dependence of the fraction of the crystalline phase x on the time t, whereas the island crystallization is described by an exponential dependence of x on t. The kinetic curves of island crystallization of amorphous films were analyzed on the basis of the α-version of the Kolmogorov model. For each type of crystallization, there are specific values of the dimensionless relative length unit δ0, which is equal to the ratio of the characteristic length unit to the parameter characterizing the unit cell of the crystal. It was established that, for the layer crystallization, the relative length unit lies in the range δ0 ~ 4300–4700, whereas for the fine-grained island crystallization, it amounts to δ0 ~ 110.

Physics of the Solid State. 2017;59(6):1225-1232
pages 1225-1232 views

Formation of the atomically ordered L10 structure with the [001] orientation during the solid-state reaction in Fe/Pd bilayer thin films

Moiseenko E.T., Altunin R.R., Zharkov S.M.

Abstract

The formation of the atomically ordered L10-FePd structure during the solid-state reaction in Fe/Pd bilayer thin films is in situ investigated by electron microscopy and electron diffraction analysis. The initial iron and palladium layers were mainly coherently oriented crystallites with the orientation relationship α-Fe (001)[110] || Pd(001)[100]. It is established that the solid-state reaction between the iron and palladium layers upon heating at a rate of 4–8°C/min starts with the formation of the FePd solid solution at 390°C; at 430°C, the formation of the atomically ordered L10-FePd structure is observed. It is shown that at the low heating rate (4–8°C/min), the L10-FePd structure with the [001] orientation relative to the film plane forms, while at the high heating rate (50°C/min) it forms with the [100], [010], and [001] orientations.

Physics of the Solid State. 2017;59(6):1233-1237
pages 1233-1237 views

A quantum-mechanical model of dilatation dipoles in topochemical synthesis of silicon carbide from silicon

Kukushkin S.A., Osipov A.V.

Abstract

The interaction between a silicon vacancy and a carbon atom formed in silicon during the topochemical synthesis of silicon carbide from silicon has been calculated using the density functional theory method. It has been shown that the silicon vacancy and the carbon atom are attracted to each other, and the strongest attraction is observed in the 〈111〉 direction. It has been established that there a qualitative agreement between the quantum-mechanical theory and the theory based on the Green’s function method for point defects. It has been concluded that the silicon vacancy and the carbon atom form a bound state in silicon. The effective stiffness coefficient of this coupling in the 〈111〉 direction has been estimated to be 5 eV/Å2.

Physics of the Solid State. 2017;59(6):1238-1241
pages 1238-1241 views

Structure and stability of defective silicene on Ag(001) and Ag(111) substrates: A computer experiment

Galashev A.E., Ivanichkina K.A., Vorob’ev A.S., Rakhmanova O.R.

Abstract

The structure and stability of a two-layer defective silicene on Ag(001) and Ag(111) substrates have been investigated using the molecular dynamics method. The transformation of the radial distribution function of silicene due to the formation of monovacancies, divacancies, trivacancies, and hexavacancies is reduced primarily to a decrease in the intensity of the peaks and the disappearance of the “shoulder” in the second peak. With the passage of time, multivacancies can undergo coalescence with each other and the fragmentation into smaller vacancies, as well as form vacancy clusters. According to the geometric criterion, the Ag(001) substrate provides a higher stability of a perfect two-layer silicene. It has been found, however, that the defective silicene on this substrate has a lower energy only when it contains monovacancies and divacancies. A change in the size of defects leads to a change in the energy priority when choosing between the Ag(001) and Ag(111) substrates. The motion of a lithium ion inside an extended channel between two silicene sheets results in a further disordering of the defective structure of the silicene, during which the strongest stresses in the silicene are generated by forces directed perpendicular to the external electric field. These forces dominate in the silicene channel, the wall of which is supported by the Ag(001) or Ag(111) substrate.

Physics of the Solid State. 2017;59(6):1242-1252
pages 1242-1252 views

Polymers

Preparation and investigation of soluble functionalized polyanilines

Biglova Y.N., Salikhov R.B., Abdrakhmanov I.B., Salikhov T.R., Safargalin I.N., Mustafin A.G.

Abstract

Soluble electron-donor conducting (co)polymers based on functionalized monomeric anilines have been synthesized and characterized for the first time. It has been shown that there is a good correlation between the results obtained from investigations of the electrochemical properties of polyaniline derivatives by the methods of cyclic voltammetry and on the basis of the temperature dependence of the electrical conductance. The polymer based on 2-(1-methyl-2-buten-1-yl)aniline has the lowest energy level of the highest occupied molecular orbital, which determines the prospects for its use as a donor in the active layer when designing organic solar cells.

Physics of the Solid State. 2017;59(6):1253-1259
pages 1253-1259 views

Graphenes

Simulation of scrolled packings of graphone nanoribbons

Savin A.V., Mazo M.A.

Abstract

A molecular mechanical model has been proposed for nanoribbons of graphone (graphene with single-sided hydrogenation), which takes into account deformations of valence bonds, valence and torsion angles, as well as non-bonded van der Waals and Coulomb interactions of atoms in a graphone nanoribbon. The ground states of the nanoribbons have been found using the proposed model. It has been shown that a rectangular fragment of graphone on a substrate formed by an infinite planar graphene sheet forms a flat monolayer, whereas a fragment that does not interact with the substrate takes a convex shape, the outer side of which contains the attached hydrogen atoms. The simulation of the dynamics has demonstrated that the single-sided structure of a graphone sheet is resistant to thermal vibrations (at temperatures T < 900 K, hydrogen atoms do not migrate from one side of the sheet to the other). The difference between the sides leads to a rapid folding of long-length free-standing graphone nanoribbons into scrolled structures. Thermal vibrations do not prevent the formation of scrolls, and the scrolls themselves are resistant to these vibrations.

Physics of the Solid State. 2017;59(6):1260-1266
pages 1260-1266 views

Negative Poisson’s ratio in a nonplanar phagraphene

Openov L.A., Podlivaev A.I.

Abstract

This paper has presented the results of the numerical simulation of the elastic properties of phagraphene—a recently predicted quasi-two-dimensional allotrope of graphene. It has been shown that the Poisson’s ratio is positive for the planar configuration of phagraphene and negative for the nonplanar configuration. Both the Poisson’s ratio and the Young’s modulus are isotropic for the planar phagraphene and are characterized by a strong anisotropy in the plane of the monolayer for the nonplanar phagraphene.

Physics of the Solid State. 2017;59(6):1267-1269
pages 1267-1269 views

Thermal Properties

High-temperature heat capacity of oxides of the CuO–V2O5 system

Denisova L.T., Belousova N.V., Denisov V.M., Galiakhmetova N.A.

Abstract

CuV2O6 and Cu2V2O7 compounds have been produced from initial components CuO and V2O5 by solid-phase synthesis. The high-temperature heat capacity of the oxide compounds has been measured using differential scanning calorimetry. The thermodynamic properties (the enthalpy change, the entropy change, and the reduced Gibbs energy) have been calculated using experimental dependences CP = f(T). It is found that there is a correlation between the specific heat capacity and the composition of oxides of the CuO–V2O5 system.

Physics of the Solid State. 2017;59(6):1270-1274
pages 1270-1274 views