Effect of Barium Codoping on Superconductivity in SrxBi2Se3

JETP Letters - A structural reason for superconductivity in a Cu-, Sr-, or Nb-atom-doped Bi2Se3 topological insulator is still unclear. To understand this reason, a codoping approach has been...     

Retrieving topology of interconnections in computational cluster based on results of MPI benchmarks

Modern computing clusters have complex interconnections between processors. The complete specification of a communication network is often insufficiently detailed. Methods for automatically refining specification are considered, which use algorithms for reconstructing the topology of connections between processors from results of benchmarking of the cluster communication network. Methods for 3D visualizing the cluster topology and for visually comparing the constructed topology with the template topology provided by the specification are also considered. The approach was tested on systems with the BlueGene P architecture and on the Lomonosov supercomputer. A greedy algorithm for retrieving the topology and an adaptation of the multidimensional scaling method for visualization are designed.     

Electronic structure and magnetic properties of RhHx (x = 0.25, 1.00, 1.33) rhodium hydrides according to the FLAPW-GGA band calculation data

The FLAPW-GGA band method is used to analyze the structural, electronic, and magnetic properties of rhodium hydrides RhH_x depending on the hydrogen content (x = 0.25, 1.00, and 1.33). The RhH monohydride is a magnetic metal. A decrease in the hydrogen content in the system or formation of vacancies in the Rh sublattice results in a transition of RhH_x to the non-magnetic state     

Isotropic and anisotropic exchange interactions in the Orbitally degenerate excited (4 A 2×2 T 2) state of a Cr3+ ion pair possessing D 3h symmetry

Experimentally observed optical absorption spectra of isolated pairs of chromium ions in Cs₃Cr₂Br₉ corresponding to transitions of pairs from the ground (⁴ A ₂ײ A ₂) state to a singly excited (⁴ A ₂ײ T ₂) state are theoretically interpreted. It is shown that the position of the exchange multiplets in the excited (⁴ A ₂ײ T ₂) state is determined mainly by the resonance exchange interactions removing the degeneracy with respect to the exchange by an excitation within the pair. It is established that the observed fine structure of the pair in the (⁴ A ₂ײ T ₂) state is due to a superposition of the contributions from the one-and two-center spin-orbit interaction and resonance antisymmetric exchange.     

Explosive chemical transformations of 4-bromo-2,4,6-tri-tert-butylcyclohexa-2,5-diene-1-one in strong uniaxial compression

Conclusions The study of explosive transformations of 4-bromo-2,4,6-tri-tert-butylcyclohexa-2,5-dien-1-one in strong uniaxial compression demonstrated the dependence of the degree of conversion of the starting substance and total yield of products on the value of the explosion pressure. A chemical mechanism of the process which includes heterolysis of the C-Br bond was proposed.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 1, pp. 137–140, January, 1989.     

Influence of carbon,nitrogen and oxygen impurities on the ductility and electronic properties of fcc iridium: First-principles study

Unusual changes in mechanical and electronic properties of fcc Ir in the presence of light sp elements (carbon, nitrogen and oxygen) as interstitial impurities have been predicted. By means of the ab initio calculations we found that, in contrast to the majority of other d metals, the ductility of iridium increases in the presence of the above impurities simultaneously with its “metallization” — owing to appreciable growth of the near-Fermi density of states.     

Evidence for higher twist mechanisms in highp ⊥π− p events with prompt ρ0 production at 38 GeV/c

The ^– p interactions with at least one charged secondary produced at polar angle 90° in c.m.s. and having the transverse momentum above 1 GeV/c were investigated. The data were obtained using streamer chamber magnetic spectrometer RISK at 38 GeV/c beam from Serpukhov accelerator. The analyzis of associated production in reconstructed events suggests, that if the transverse momentum of a pair of oppositely charged secondaries compensates the trigger particlep practically completely, this pair is the product of the ⁰ decay in marked fraction of such events. We observed a large spin-alignment for the ⁰-mesons selected as described above: the probability of zero spin projection onto the normal to the ⁰ production plane is equal to ₀₀ ^T =0.86±0.23. The enhancement of the number of events, in which the ⁰ picks up practically full momentum transfer carrying by the exchange, and also the enlarged tensor polarization for the ⁰-mesons in these events could be qualitatively explained as manifestation of direct ⁰-production via the QCD higher twist processes in the highp ^– p collisions. At the same time, the observed effects are markedly larger than the values predicted with QCD model in which the higher twist corrections were included.     

Temperature breaking of hydrogen bonds in ammonia studied by π−-meson capture in hydrogen

The capture probability of stopped π^? mesons by hydrogen atoms of ammonia increases with temperature in the liquid phase but in the supercritical phase it is temperature-independent. This can be attributed to the temperature breaking of hydrogen bonds. Rough estimates are given for the fraction of broken hydrogen bonds at various temperatures.     

Stability,structural, elastic and electronic properties of RuN polymorphs from first-principles calculations

First-principles FLAPW–GGA calculations for six possible polymorphs of ruthenium mononitride RuN indicate that the most stable structure is that of zinc blende rather than the rock salt structure recently reported for synthesized RuN samples. The elastic, electronic properties and the features of chemical bonds of zinc-blende RuN polymorph were investigated and discussed in detail.