Lattice dynamics in heavy rare-gas crystals under pressure

The lattice dynamics of compressed rare-gas crystals is theoretically investigated within the ab initio approach in the framework of the Tolpygo model, which explicitly includes the deformation of electron shells in the dipole approximation. The phonon frequencies of compressed rare-gas crystals are calculated with allowance made for the electron-phonon interaction at the mean-value points with the use of the dynamic matrix constructed with the ab initio short-range repulsive potential. The energy of zero-point vibrations and the heat capacity of compressed krypton and xenon face-centered cubic crystals are calculated in the harmonic approximation. The calculated temperature dependences of the specific heat capacity and the Debye temperature are in good agreement with the data available in the literature on the experiment at zero pressure and the results of the calculations within the density-functional theory for all pressures. The quantum effects, in particular, the energies E _zp of zero-point vibrations for krypton and xenon crystals, are investigated at different pressures.     

Structure and properties of copper coatings electrodeposited under X-ray radiation

142-145The influence of X-ray radiation of different wave lengths on the structure and properties of electrodeposited copper coatings is found. It is determined by the methods of X-ray structure analysis and optical and scanning microscopy that, in the process of electrodeposition, X-ray radiation changes the primary structure of electrolyte and leads to a decrease in the grain size of deposits and an increase in the microhardness and degree of dispersion of mosaic blocks. The radiation effect on the process of electrodeposition is accompanied by an increase in the rate of material deposition on the cathode due to intensification of the diffusion of electrolyte components to the cathode.     

Modification of the superconducting order parameter Δ(k) by long-range interactions

It is demonstrated that the inclusion of long-range intersite interactions qualitatively modifies the dependence of a superconducting gap on quasimomentum for both s-and d-symmetry types. In particular, the order parameter of a superconducting phase with $d_{x^2 - y^2 } $ the symmetry type depends on two amplitudes and has the form Δ(k)=Δ₁(cosk _x ?cosk _y )+Δ₂(cos2k _x ?cos2k _y ). In this case, the theoretical dependence of the critical temperature on the degree of doping agrees with the experimental dependence.     

Dielectric Spectra and d-bands Structure of Germanium,Tin, and Lead Tellurides

Russian Physics Journal - The known experimental absorption spectra were used to calculate the dielectric spectra of GeTe, SnTe, and PbTe crystals in the region of electron transitions from the...     

Effects of electron inelastic transport through the potential relief of a spin dimer in a magnetic field

The influence of inelastic effects on electron quantum transport through the potential relief of a dimer system was studied by exact solution of the Schrodinger equation. The nature of this problem is due to the coherent superposition of the different potential profiles through which the spin-polarized electron tunnels. It was found that the low magnetic field initiates new peaks of resonant tunneling. In high magnetic fields, the transport of electrons with opposite spin polarization is qualitatively different.     

Effective interactions and the nature of Cooper instability of spin polarons in the 2D Kondo lattice

It has been shown that two-and three-center interactions arise in the strong-coupling regime for the 2D Kondo lattice; these interactions both induce and suppress the Cooper instability. It is important that, in contrast to the t-J* model, the three-center interactions promote the Cooper pairing and ensure the appearance of the superconducting phase with a high critical temperature T _c. The calculated concentration dependences of T _c agree well with the experimental data for the cuprate superconductors.     

Pickering emulsion polymerization of polyaniline/LiCoO2 nanoparticles used as cathode materials for lithium batteries

The oil in water (o/w) emulsions were prepared using aniline dissolved in toluene and LiCoO₂ particles as stabilizers (Pickering emulsions). Pickering emulsions are stabilized by adsorbed solid particles instead of emulsifier molecules. The mean droplet diameter of emulsions was controlled by the mass ratio M (oil)/M (solid particles). The emulsions showed great stability during 3 days. The composite materials containing LiCoO₂ and the conductive polymer polyaniline (PANI) have been prepared by means of polymerization of aniline emulsion stabilized by LiCoO₂ particles. The composite materials were characterized by nanosphere and nanofiber-like structures. The nanofiber-like morphology of the powdered material was distinctly different of the morphologies of the parent materials. The electrochemical reactivity of PANI/LiCoO₂ composites as positive electrode in a lithium battery was examined during lithium ion deinsertion and insertion by galvanostatic charge–discharge testing; PANI/LiCoO₂ (1:4) composite materials exhibited the best electrochemical performance by increasing the reaction reversibility and capacity compared to that of the pristine LiCoO₂ cathode. The first discharge capacity of PANI/LiCoO₂ (1:4) was 167 mAh/g, while that of LiCoO₂ was136 mAh/g.     

Public perception of nanotechnology

While several studies on the public opinion of nanotechnology have pointed to a rather enthusiastic U.S. public, the public uptake of nanotechnology in Europe is more contained. The results of the Swiss publifocus on nanotechnology reveal a pragmatic attitude of citizens toward the emerging technologies, thus confirming what has been identified as a “balanced approach” in the NanoJury UK.

Study of Electrical Conductivity of Para-Toluene Sulfonic Acid Doped Polyaniline/Polyester-Based Polyurethane Blends in the S-Band Frequency Range

Conducting polymer blends were prepared using polyaniline doped with para- toluene sulfonic acid (PTSA-PANI) and a polyester polyol-based polyurethane (PU). The morphological, thermal and dielectric properties of the PTSA-PANI/PU blends in the frequency range of 1–5 GHz (S band) were investigated. It was found that the morphology of the samples was affected by the PTSA-PANI loading, resulting in the formation of agglomerates and pathways when above 10 wt%. The thermal stability of the composites was improved with increased PTSA-PANI loading. The electrical conductivity percolation threshold was obtained at 2.5% of PTSA-PANI loading and the electrical conductivity reached the value of 0.13 S/m at a PTSA-PANI loading of 30 wt%. The obtained results for the PTSA-PANI/PU blends prepared indicate a high potential for their successful use in electrical and electromagnetic applications.     

Coulomb repul sion of hole s and competition between $${d_{{x^2} - {y^2}}}$$ -wave and s-wave paring s in cuprate superconductor s

The effect of the Coulomb repulsion of holes on the Cooper instability in an ensemble of spin–polaron quasiparticles has been analyzed, taking into account the peculiarities of the crystallographic structure of the CuO₂ plane, which are associated with the presence of two oxygen ions and one copper ion in the unit cell, as well as the strong spin–fermion coupling. The investigation of the possibility of implementation of superconducting phases with d-wave and s-wave of the order parameter symmetry has shown that in the entire doping region only the d-wave pairing satisfies the self-consistency equations, while there is no solution for the s-wave pairing. This result completely corresponds to the experimental data on cuprate HTSC. It has been demonstrated analytically that the intersite Coulomb interaction does not affect the superconducting d-wave pairing, because its Fourier transform V _q does not appear in the kernel of the corresponding integral equation.