Band structure of (Sr3Sc2O5)Fe2As2 as a possible parent phase for new FeAs superconductors

By means of first-principles FLAPW-GGA calculations, we have investigated the electronic properties of the newly synthesized layered phase - (Sr3Sc2O5)Fe2As2. The electronic bands, density of states and Fermi surface have been evaluated. The resembling of our data for (Sr3Sc2O5)Fe2As2 with band structure pictures of known FeAs superconducting materials may be considered as the theoretical background specifying the possibility for (Sr3Sc2O5)Fe2As2 to become a parent phase for new FeAs superconductors.Comment: 10 pages, 4 figures, 3 table

Investigation of industrial compositions SONKOR as corrosion inhibitors of mild steel in neutral media containing hydrogen sulfide

Electrochemical and corrosion behavior of mild steel in neutral media containing hydrogen sulfide has been investigated by weight-loss and electrochemical methods and protective effect of industrial compositions SONKOR has been determined. It has been shown that in 3 % NaCl compositions SONKOR have weak protective effect but it increases greatly in presence of hydrogen sulfide in the solution. At concentration of H2S = 0,6 gram per liter maximal protective effect has SONKOR 9801 (85.57 %) and SONKOR 9920А (81.97 %). Inhibitors SONKOR 9021С (70.82 %), 9510А (73.11 %) и 9701 (67.87 %) show less protective effect

The impedance of anodic processes on passive NiSi-electrode in sulfuric fluoride containing electrolyte

The mechanism and kinetics of anodic oxidation of the Ni-Si electrode in solutions of 0.5 M H2SO4 + (0,005 – 0,05)M NaF in the passive state were investigated by methods of polarization and impedance measurements. The impedance spectra are interpreted on the assumption about the formation of the bilayer oxide film on the surface of the silicide nickel, the outer layer which has a porous structure. The growth of the porous layer with the increase of the electrode potential in the investigated solutions is linearly (constant anodizing is 2.2 nm/V). The increase in NaF concentration leads to a decrease in the thickness of the porous layer. The growth of the barrier layer of the oxide film was described in the framework of the model of point defects. The diffusion coefficient of oxygen vacancies inside the barrier layer of the film is 8.5 · 10–16 cm2/s and varies weakly with the potential and the content of sodium fluoride in solution. Microscopic and profilometric studies show the development of the surface of the NiSi electrode during anodic etching.The work is executed at financial support of RFBR under research project No. 14-03-31016

Soil water retention curve of agrogray soils: influence of anisotropy and the scaling factor

The soil water characteristic or soil water retention curve (WRC) of medium-loamy gray forest soil horizons was studied in cylinder-shaped samples of disturbed and undisturbed structure. The sample height varied within 2-4 cm and the diameter within 4.5-10 cm. The soil monoliths were sampled in three profiles: vertically, along the slope, and across the slope in accordance with the intrasoil paleorelief formed by the fun-nel-shaped surface of the second humus horizon. The experimental WRC were approximated with the van Genuchten equatio

On Electron Transport in ZrB12, ZrB2 and MgB2

We report on measurements of the temperature dependence of resistivity, $\rho(T)$, for single crystal samples of ZrB$_{12}$, ZrB$_{2}$ and polycrystalline samples of MgB$_{2}$. It is shown that cluster compound ZrB$_{12}$ behaves like a simple metal in the normal state, with a typical Bloch -- Gr\"uneisen $\rho(T)$ dependence. However, the resistive Debye temperature, $T_{R}=300 K$, is three times smaller than $T_{D}$ obtained from specific heat data. We observe the $T^{2}$ term in $\rho(T)$ of these borides, which could be interpreted as an indication of strong electron-electron interaction. Although the $\rho (T)$ dependence of ZrB$_{12}$ reveals a sharp superconductive transition at $T_{c}=6.0 K$, no superconductivity was observed for single crystal samples of ZrB$_{2}$ down to $1.3 K$.Comment: 5 pages, 4 figure

Effects of Ru Substitution on Dimensionality and Electron Correlations in Ba(Fe_{1-x}Ru_x)_2As_2

We report a systematic angle-resolved photoemission spectroscopy study on Ba(Fe$_{1-x}$Ru$_x$)$_2$As$_2$ for a wide range of Ru concentrations (0.15 $\leq$ \emph{x} $\leq$ 0.74). We observed a crossover from two-dimension to three-dimension for some of the hole-like Fermi surfaces with Ru substitution and a large reduction in the mass renormalization close to optimal doping. These results suggest that isovalent Ru substitution has remarkable effects on the low-energy electron excitations, which are important for the evolution of superconductivity and antiferromagnetism in this system.Comment: 4 pages, 4 figure

Electron transport, penetration depth and upper critical magnetic field of ZrB12 and MgB2

We report on the synthesis and measurements of the temperature dependence of resistivity, R(T), the penetration depth, l(T), and upper critical magnetic field, Hc2(T), for polycrystalline samples of dodecaboride ZrB12 and diboride MgB2. We conclude that ZrB12 as well as MgB2 behave like simple metals in the normal state with usual Bloch-Gruneisen temperature dependence of resistivity and with rather low resistive Debye temperature, TR=280 K, for ZrB12 (as compared to MgB2 with TR=900 K). The R(T) and l(T) dependencies of ZrB12 reveal a superconducting transition at Tc=6.0 K. Although a clear exponential l(T)dependence in MgB2 thin films and ceramic pellets was observed at low temperatures, this dependence was almost linear for ZrB12 below Tc/2. These features indicate s-wave pairing state in MgB2, whereas a d-wave pairing state is possible in ZrB12. A fit to the data gives a reduced energy gap 2D(0)/kTc=1.6 for MgB2 films and pellets, in good agreement with published data for 3D \pi - sheets of the Fermi surface. Contrary to conventional theories we found a linear temperature dependence of Hc2(T) for ZrB12 (Hc2(0)=0.15 T).Comment: 8 pages, 10 figures, submitted to JET

Band structure of new superconducting AlB_2-like ternary silicides M(Al_{0.5}Si_{0.5})_2 and M(Ga_{0.5}Si_{0.5})_2 (M= Ca, Sr and Ba)

The electronic band structures of the new superconducting (with T_c up to 7.7K) ternary silicides M(A_{0.5}Si_{0.5})_2 (M= Ca, Sr, Ba; A= Al, Ga) in the AlB_2-type structure have been investigated using the full-potential LMTO method. The calculations showed that the trend in transition temperatures doesn't follow the changes in the density d-states at the Fermi level and probably is associated with phonon-mode frequencies.Comment: 7 pagers, 1 table, 7 figure