Disproportionation of nonoxygenated U(V) bound in the complex with heteropoly anions P<Subscript>2</Subscript>W<Subscript>17</Subscript>O<Stack><Subscript>61</Subscript><Superscript>10−</Superscript></Stack>

The effect of experimental conditions on U^VL₂ (1–2 mM) disproportionation was studied spectrophotometrically through the U^IVL₂ accumulation (L = P₂W₁₇O ₆₁ ^10? ). In 1 M NaNO₃ solution containing 0.01 M HAc and 0.01 M NaAc, the rate of U^VL₂ disappearance is described by the equation V = k ₁[U^VL₂]. The k ₁ value is almost constant with pH decreasing from 4.5 to 1.7, but increases with increasing acetate concentration; the presence of 1 mM U^IVL₂, U(VI), or L does not affect k ₁. In the solutions of 0.1–1.0 M HClO₄ (ionic strength 1), the reaction rate is described by the equation V = 2k ₂[H⁺]^2.5[U^VL₂]². Probable disproportionation mechanism is discussed. The first stage is substitution of L by water molecules in the U^IVL₂ complex and appearance of the reactive U(V) complex with mixed coordination sphere.     

Electronic and Ferromagnetic Properties of 3<Emphasis Type="Italic">d</Emphasis>(V)-Doped (BaS) Barium Sulfide

The objective of this study is to investigate the electronic structure and ferromagnetic properties of barium sulfide (BaS) doped with vanadium (V) impurity. The calculations were performed by using the first-principle calculations of density functional theory. The lattice constant of Ba_1?x V _x S decreases with increasing concentration (x) of the V atom. We have found that the Ba_0.75 V _0.25S and Ba_0.5 V _0.5S compounds are half-metallic ferromagnets with total magnetic moments of 3 μ _B per V atom, while for high concentration x = 0.75, the Ba_0.25 V _0.75S becomes nearly half metallic due to broadening of 3d (V) states in the gap. The exchange coupling between the 3d (V) levels and conduction bands is ferromagnetic, confirming the magnetic nature of Ba_1?x V _x S compounds.     

Spatial and Quantum Confinement of Si Nanoparticles Deposited by Laser Electrodispersion onto Crystalline Si

C–V characteristics and DLTS spectra of heterostructures made up of layers of closely packed amorphous Si nanoparticles deposited by laser electrodispersion onto single-crystal p-Si substrates have been examined. The patterns observed in the behavior of the C–V characteristics and DLTS spectra measured in the dark and under illumination with white light at various bias pulse voltages U _b and filling pulse voltages U _f suggest that the spatially localized amorphous Si nanoparticles have an average size of less than 2 nm, which is comparable with the de Broglie electron wavelength, and are characterized by quantum confinement. The ground and excited states of quantum dots are formed and exhibit the Stark effect and effects of electricdipole and controllable metastable occupancy under illumination.     

On the Interpretation of Near-Critical Gas–Liquid Heat Capacities by L. V. Woodcock,Int. J. Thermophys. (2017) 38, 139: Comments

It is shown that: (1) the expressions for the isochoric (C_V) and isobaric (C_P) heat capacities of liquid and gas, coexisting in phase equilibrium, the heat capacities at saturation of liquid and gas (C_σ) and the heat capacity C_λ used in the article “On the Interpretation of Near-Critical Gas–Liquid Heat Capacities, L. V. Woodcock, Int. J. Thermophys. (2017) 38, 139” are incorrect; (2) the conclusions of the article based on the comparison of the incorrect C_V, C_P and C_λ with experimental data are also incorrect; (3) the lever rule cannot be used to define C_V and C_P in the two-phase coexistence region; (4) a correct expression for the isochoric heat capacity describes well the experimental data; (5) there is no misinterpretation of near-critical gas–liquid heat capacity measurements in the two-phase coexistence region; (6) there are no proofs in the article that: (a) the divergence of C_V is apparent; (b) it has not been established experimentally that the thermodynamic properties of fluids satisfy scaling laws with universal critical exponents asymptotically close to a single critical point of the vapor–liquid phase transition; and (c) there is no singular critical point on Gibbs density surface. We obtained the relations connecting the isochoric heat capacity in the two-phase region with thermodynamic properties at saturation of homogeneous liquid and gas which can be used to verify the equation of state.     

First-Principle Study of Electronic and Half-Metallic Ferromagnetic Properties of Vanadium (V)-Doped Cubic BP and InP

In this study, we use the first-principle calculations of density functional theory with gradient generalized approximation of Wu–Cohen to investigate the doping effect of vanadium impurity on structural, electronic and magnetic properties of In_1?x V _x P and B_1?x V _x P alloys at various concentrations x = 0.0625, 0.125 and 0.25. Owing to the metallic nature of majority spin and semiconducting minority spin, the In_1?x V _x P compounds exhibit a half-metallic character with total magnetic moments of 2 μ _B, while the B_1?x V _x P has metallic nature for all concentrations. The results of exchange parameters revealed that exchange coupling between vanadium atoms and the conduction band is ferromagnetic, confirming the magnetic feature of In_1?x V _x P and B_1?x V _x P. From our findings, we have predicted that the In_1?x V _x P alloys seem to be potential materials for spintronics.     

Insight into Structural,Electronic, Magnetic,Mechanical, and Thermodynamic Properties of Actinide Perovskite BaPuO<Subscript>3</Subscript>

In this paper, we have performed a systematic investigation on structural, magnetic, electronic, mechanical, and thermodynamic properties of BaPuO₃ perovskite within density functional theory (DFT) using generalized gradient approximations (GGA), onsite coulomb repulsion (GGA + U), and modified Becke-Johnson (mBJ). The calculated structural parameters were found in good agreement with the experimental results. A large value of magnetic moment equal to integer value of 4 μ_B was obtained for the compound. The spin-polarized electronic band structure and density of states present 100% of spin polarization at Fermi level, resulting in half-metallic nature for the compound with spin-up states as metallic and spin- down states as a semiconducting. The elastic and mechanical properties have also been predicted. Moreover, we have calculated thermodynamic properties like Debye temperature (??_D), specific heat (C_V), entropy (S), etc. using quasi-harmonic Debye model.     

Effects of Iron Contents on the Vortex State in Fe<Subscript><Emphasis Type="Italic">x</Emphasis></Subscript>Se<Subscript>0.5</Subscript>Te<Subscript>0.5</Subscript>

We investigate the effects of iron content on the upper critical field (H _c2) and the activation energy U(T) in thermally activated flux flow in Fe _x Se_0.5Te_0.5 near the superconducting transition temperature T _c . The variations in H _c2(T) with temperature are analyzed using Ginzburg-Landau (GL), Werthamer-Helfand-Hohenberg (WHH) models along with the empirical relation (ER). The obtained values of H _c2(0) depend strongly on the model and the criteria used to determine the transition temperature. However, the general trend is that that H _c2(0) increases with the increasing Fe content. The activation energy U(T) is maximum for x =? 1 and rapidly suppressed by excess or deficiency of iron. The low values of U(T) (～10 meV) reflect the low vortex-pinning nature (due to defects, vacancies, etc.) in the Fe _x Se_0.5Te_0.5 superconductor.     

Kinetics of gas-phase conversion of U<Subscript>3</Subscript>O<Subscript>8</Subscript> into water-soluble compounds in nitrating atmosphere at 25–30°С

The kinetics of the gas-phase conversion of U₃O₈ in NO_x–H₂O (vapor)–air and HNO₃ (vapor)–H₂O (vapor)–air atmospheres was fitted by the Kazeev–Kolmogorov–Erofeev equation. The following parameters n and K were obtained: for experiments in NO_x–H₂O (vapor)–air atmosphere, n = 0.2 ± 0.1 and K = 0.2 ± 0.2 h^–1; for experiments in HNO₃ (vapor)–H₂O (vapor)–air atmosphere, n = 0.3 ± 0.2 and K = 0.03 ± 0.02 h^–1 (confidence probability p = 0.95). For the U₃O₈ conversion in both media, n < 0.5, which suggests the diffusion control of the U₃O₈ conversion under the action of both HNO₃ and NO_x.     

Extended BCS-Bose Crossover

Applying the generalized Bose-Einstein condensation (GBEC) formalism, we extend the BCS-Bose crossover theory by explicitly including hole Cooper pairs (2hCPs). From this, follows a phase diagram with two pure phases, one with 2hCPs and the other with electron Cooper pairs (2eCPs), plus a mixed phase with arbitrary proportions of 2eCPs and 2hCPs. The special-case phase when there is perfect symmetry, i.e., with ideal 50-50 proportions between 2eCPs and 2hCPs, corresponds to the usual BCS-Bose crossover. Explicitly including 2hCPs yields an extended BCS-Bose crossover which predicts improved T _c /T _F values for some conventional superconductors (i.e., with electron-phonon dynamics) when compared with experiment. To do this, we employ the BCS dimensionless coupling constant λ _{B C S} via the BCS gap equation and compare with the Bogoliubov et al. upper limit λ _{B C S} ≤ 1/2. Another phase diagram presented exhibits experimental T _c /T _F values for some conventional superconductors for arbitrary proportions between 2eCPs and 2hCPs as function of Δn = n/n _f ? 1, where n is the electron concentration and n _f that of unbound electrons at T = 0. The extended crossover is compared with experimental T _c /T _F values as well as to the gap-to- T _c ratio.     

A Novel Theoretical Investigation of Electronic Structure and Half-Metallic Ferromagnetism in 3d (V)-Doped InP for Spintronic Applications

We have investigated the electronic structure and half-metallic ferromagnetic properties of vanadium (V)-doped InP indium phosphide in the zinc blende structure as ternary In _1?x V _x P compounds at concentrations x = 0.25, 0.5, and 0.75 of V, using first-principles calculations of density functional theory with generalized gradient approximation functional of Wu and Cohen (GGA-WC). It is found that In _0.75 V _0.25P, In _0.5 V _0.5P, and In _0.25 V _0.75P compounds depicted a half-metallic (HM) ferromagnetic character with spin polarization of 100 % at Fermi level. The HM ferromagnetic behavior is confirmed by the integral Bohr magneton of total magnetic moment of 2 μ _B per V atom of In _1?x V _x P, which mainly arises from the 3d (V) states along with less important contributions of induced local magnetic moments at In and P sites. Therefore, the In _1?x V _x P material seems to be potential candidate for possible semiconductor spintronics applications.     

Characteristics of Superconducting State in Vanadium: the Eliashberg Equations and Semi-analytical Formulas

The superconducting state in vanadium characterizes with the critical temperature (T _c ) equal to 5.3 K. The Coulomb pseudopotential, calculated with the help of the Eliashberg equations, possesses anomalously high value μ ^?(3Ω_max) = 0.259 or μ ^?(10Ω_max) = 0.368 (Ω_max denotes the maximum phonon frequency). Despite the relatively large electron-phonon coupling constant (λ = 0.91), the quantities such as the order parameter (Δ), the specific heat (C), and the thermodynamic critical field (H _c ) determine the values of the dimensionless ratios not deviating much from the predictions of the BCS theory: R _Δ = 2Δ(0)/k _B T _c = 3.68, R _C = ΔC(T _c ) /C ^N (T _c ) = 1.69, and \(R_{H}=T_{c}C^{N}\left (T_{c}\right )\slash {H^{2}_{c}}\left (0\right )=0.171\). This result is associated with the reduction of the strong-coupling and the retardation effects by the high value of the Coulomb pseudopotential. It has been shown that the results of the Eliashberg formalism can be relatively precisely reproduced with the help of the semi-analytical formulas, if the value of μ ^? is determined on the basis of the T _c -Allen-Dynes expression (μ A D? = 0.198). The attention should be paid to the fact that in the numerical and in the semi-analytical approach the comparable values of the thermodynamic parameters for the same μ ^? have been obtained only in the vicinity of the point μ ^? = 0.1.     

The Effect of Using Different Y<Subscript>2</Subscript>O<Subscript>3</Subscript> Layers on the Activation Energy and Irreversibility Line of MPMG YBCO Bulk at 1050 °C Growth Temperature

In this study, three kinds of YBCO samples which are named Y1, Y2 and Y3 were fabricated by a melt–powder–melt–growth (MPMG) method. The Y1 sample was placed into a platinum (Pt) crucible without Y₂O₃, the Y2 sample was located on a Al₂O₃ crucible with a freely poured Y₂O₃ powder and the Y3 sample was located on a Al₂O₃ crucible with a 1-mm-thick buffer layer of Y₂O₃. YBCO samples were investigated by magnetoresistivity (ρ–T) measurements in dc magnetic fields (parallel to the c-axis) up to 5 T. The effect of the Y₂O₃ layer on the activation energy and irreversible flux of the samples was studied. The activation energies (U) were determined using the Arrhenius activation energy law from ρ–T. The power law relationship for U with H^?α was investigated. α was calculated to find out which defects were dominant in the samples. Irreversibility fields (H_irr) and upper critical fields (H_c2) were obtained using 10 and 90% criteria of the normal-state resistivity value from ρ–T curves. Irreversibility lines (ILs) were estimated from the equation H_irr ～ (1 ? T_irr(H)/T_irr(0))ⁿ. The fitting results to giant flux creep and vortex glass models were discussed.     

Structural investigation of V<Subscript>2</Subscript>O<Subscript>5</Subscript>–P<Subscript>2</Subscript>O<Subscript>5</Subscript>–K<Subscript>2</Subscript>O glass system with antibacterial potential

The xV₂O(1?x)[0.8 P₂O₅ ? 0.2 K₂O] glass system with 0 ≤ x ≤ 50 mol% was prepared and the structural changes induced in these glasses by increasing the vanadium oxide content were investigated by IR and ESR spectroscopies. The dual behaviour role of V₂O₅ oxide, as network modifier (for x ≤ 10 mol%) and the network former (x ≥ 20 mol%), as a consequence of phosphate network depolymerization and P–O–V and V–O–V linkages appearance was also highlighted. The antibacterial effect of the glasses with x ≤ 20 mol% V₂O₅ content was tested by optical density (OD) measurements. A linear correlation between the amount of vanadium and the antibacterial effect was evidenced.     

New Class of High-<Emphasis Type="Italic">T</Emphasis><Subscript>C</Subscript> Diluted Ferromagnetic Semiconductors Based on CaO without Transition Metal Elements

We propose new-type ferromagnetic semiconductors based on CaO and K₂S without any transition metal elements. These materials show transparent and half-metallic ferromagnetism if the deep-impurity-band width (W) induced by doping of C, N, Si, or Ge impurities, and the electron-correlation energy (U) satisfy the Stoner’s condition of highly correlated electron system (U>W). Based on our first-principles calculations, we demonstrate that these materials satisfy the Stoner’s condition, and could be new candidates for transparent and half-metallic DMSs.     

Magnetic Entropy Change by Mean-Field Theory for the Second-Order Phase Transition Manganite Nd<Subscript>0.6</Subscript>Sr<Subscript>0.3</Subscript>Ca<Subscript>0.1</Subscript>Mn<Subscript>0.975</Subscript>Fe<Subscript>0.025</Subscript>O<Subscript>3</Subscript>

In this work, we are going to show the method based on mean-field scaling for the Nd_0.6Sr_0.3Ca_0.1Mn_0.975Fe_0.025 O₃ sample, where from scaling of experimental magnetization data, the mean-field exchange parameter λ and the f function of the equation of state \(M(T,H)=B_{S} [\frac {\left ({H+H_{\text {ex}}} \right )}{T}]\) are directly determined. The scaling approach allows finding the dependence of H _ex on T or higher powers of M, which determine the order of the phase transition. Quantum spin number has been determined. In this study, we use \(\left | {\Delta S_{M} (T)} \right |\) obtained from isothermal magnetization measurements; we compare this result to mean-field theory fittings from a novel scaling method through the use of theoretical results S, g, and λ. The obtained results by mean-field theory are suitable and in good agreement with the classical Maxwell relation.     

Appearance of Superconductivity at 15.9 K in Layered V<Subscript>2</Subscript>AlN

A bulk polycrystalline sample with the nominal compositions represented by V₂AlN_1?δ was synthesized by a two-step solid-state reaction. The structural characterization has been done via X-ray diffraction, followed by Rietveld refinements, which revealed that the layered V₂AlN is crystalized in cubic Fm3m space group with lattice parameters a = b = c = 6.127 Å. Both DC resistivity and magnetization measurements confirmed that V₂AlN is a bulk superconductor with superconducting transition temperature (T _c ) of 15.9 K.     

Methods of Extracting Current Density Dependence of the Effective Activation Energy <Emphasis Type="Italic">U</Emphasis><Subscript>eff</Subscript>(J) in High <Emphasis Type="Italic">T</Emphasis><Subscript>c</Subscript> Superconductors

We have reviewed the methods of extracting current density dependence of the effective activation energy U_eff(J) from experimental data, including transport measurements and magnetic relaxations. Then we applied the method proposed by Maley etc. on our single-phase HgBaCaCuO-1223 sample to obtain the effective activation energy. The effective activation energy U_eff(J, H = 1~T) is extracted from the magnetization relaxation data. On the other hand, U_eff(J) can be theoretically estimated for the model of a sinusoidal washboard potential in superconductors. By comparing the two results we believe that the single curve obtained in the former way can be seen as real current density dependence of effective activation energy U_eff(J). In addition, we have analyzed the reasons why the magnetic decay data at various temperatures can be scaled onto a single curve. The pinning mechanism in the measured temperature range does not change, and the activation energy depends separately on the three variables: T, B, and J are thought as two important factors for this. In the temperature close to zero and near T_c, thermally assisted flux motion would no longer valid since other processes predominate.     

Stability of the Supercon ducting d-Wave Pairing Towar d the Intersite Coulomb Repulsion in $$\hbox {CuO}_2$$ Plane

Taking into account the real crystalline structure of the \(\hbox {CuO}_2\) plane and the strong spin-fermion coupling, we study the influence of the intersite Coulomb repulsion between holes on the Cooper instability of the spin-polaron quasiparticles in cuprate superconductors. The analysis shows that only the superconducting d-wave pairing is implemented in the whole region of doping, whereas the solutions of the self-consistent equations for the s-wave pairing are absent. It is shown that intersite Coulomb interaction \(V_1\) between the holes located at the nearest oxygen ions does not affect the d-wave pairing, because its Fourier transform \(V_q\) vanishes in the kernel of the corresponding integral equation. The intersite Coulomb interaction \(V_2\) of quasiparticles located at the next-nearest oxygen ions does not vanish in the integral equations, however, but it is also shown that the d-wave pairing is robust toward this interaction for physically reasonable values of \(V_2\).     

Experimental Study of the Thermodynamic Properties of Diethyl Ether (DEE) at Saturation

The isochoric heat capacities \({({C_{V1}^{\prime}} ,{C_{V1}^{\prime\prime}},{C_{V2}^{\prime}},{C_{V2}^{\prime\prime}})}\), saturation densities (\({\rho _{\rm S}^{\prime}}\) and \(({\rho_{\rm S}^{\prime\prime})}\)), vapor pressures (P _S), thermal-pressure coefficients \({\gamma_V=\left({\partial P/\partial T}\right)_V}\), and first temperature derivatives of the vapor pressure γ _S = (dP _S/dT) of diethyl ether (DEE) on the liquid–gas coexistence curve near the critical point have been measured with a high-temperature and high-pressure nearly constant-volume adiabatic piezo-calorimeter. The measurements of \({({C_{V1}^{\prime}} ,{C_{V1}^{\prime\prime}},{C_{V2}^{\prime}},{C_{V2}^{\prime\prime}})}\) were made in the liquid and vapor one- and two-phase regions along the coexistence curve. The calorimeter was additionally supplied with a calibrated extensometer to accurately and simultaneously measure the PVT, C _V VT, and thermal-pressure coefficient, γ _V , along the saturation curve. The measurements were carried out in the temperature range from 416 K to 466.845 K (the critical temperature) for 17 liquid and vapor densities from 212.6 kg · m^?3 to 534.6 kg · m^?3. The quasi-static thermo- (reading of PRT, T ? τ plot) and baro-gram (readings of the tensotransducer, P ? τ plot) techniques were used to accurately measure the phase-transition parameters (P _S ,ρ _S ,T _S) and γ _V . The total experimental uncertainty of density (ρ _S), pressure (P _S), temperature (T _S), isochoric heat capacities \({({C_{V1}^{\prime}} ,{C_{V1}^{\prime\prime}},{C_{V2}^{\prime}},{C_{V2}^{\prime\prime}})}\), and thermal-pressure coefficient, γ _V , were estimated to be 0.02 % to 0.05 %, 0.05 %, 15 mK, 2 % to 3 %, and 0.12 % to 1.5 %, respectively. The measured values of saturated caloric \({({C_{V1}^{\prime}} ,{C_{V1}^{\prime\prime}},{C_{V2}^{\prime}},{C_{V2}^{\prime\prime}})}\) and saturated thermal (P _S, ρ _S, T _S) properties were used to calculate other derived thermodynamic properties C _P , C _S, W, K _T , P _int, ΔH _vap, and \({\left({\partial V/\partial T}\right)_P^{\prime}}\) of DEE near the critical point. The second temperature derivatives of the vapor pressure, (d² P _S/dT ²), and chemical potential, (d² μ/dT ²), were also calculated directly from the measured one- and two-phase liquid and vapor isochoric heat capacities \({({C_{V1}^{\prime}} ,{C_{V1}^{\prime\prime}},{C_{V2}^{\prime}},{C_{V2}^{\prime\prime}})}\) near the critical point. The derived values of (d² P _S/dT ²) from calorimetric measurements were compared with values calculated from vapor–pressure equations. The measured and derived thermodynamic properties of DEE near the critical point were interpreted in terms of the “complete scaling” theory of critical phenomena. In particular, the effect of a Yang–Yang anomaly of strength R _μ on the coexistence-curve diameter behavior near the critical point was studied. Extended scaling-type equations for the measured properties P _S (T), ρ _S (T), and \({({C_{V1}^{\prime}} ,{C_{V1}^{\prime\prime}},{C_{V2}^{\prime}},{C_{V2}^{\prime\prime}})}\) as a function of temperature were developed.     

Magnetic-Memory Effects in High-Purity Beryllium

We study the magnesium-thermal beryllium condensate in the course of natural aging after several procedures of treatment by weak constant magnetic fields. The amplitude-time dependences of the effective shear modulus (G _ef ~ f ²), low-frequency internal friction, the parameter r, and the ratio of dislocation velocities V _afef /V ₀ are analyzed. It was revealed that the hysteresis in the f ²(γ) curves disappears after ~120 h of natural aging and the sign of r(γ) and V _afef /V ₀(γ) is inverted. The nature of the detected effects is connected with the appearance of microcracks in the stage of elastic deformation and their healing as a result of the viscous motion of unpinned dislocations in the field of point defects in the basal slip plane.