First Principles Study of the Electronic and Vibrational Properties of LiNbO2

In the layered transition metal oxide LiNbO$_2$ the Nb$^{3+}$ ($4d^2$) ion is trigonal-prismatically coordinated with O ions, with the resulting crystal field leading to a single band system for low energy properties. A tight-binding representation shows that intraplanar second neighbor hopping $t_2 = 100$ meV dominates the first neighbor interaction ($t_1 = 64$ meV). The first and third neighbor couplings are strongly modified by oxygen displacements of the symmetric Raman-active vibrational mode, and electron-phonon coupling to this motion may provide the coupling mechanism for superconductivity in Li-deficient samples (where $T_c = 5$ K). We calculate all zone-center phonon modes, identify infrared (IR) and Raman active modes, and report LO-TO splitting of the IR modes. The Born effective charges for the metal ions are found to have considerable anisotropy reflecting the degree to which the ions participate in interlayer coupling and covalent bonding. Insight into the microscopic origin of the valence band density, composed of Nb $d_{z^2}$ states with some mixing of O $2p$ states, is obtained from examining Wannier functions for these bands.Comment: 12 pages, 7 figures; Updated with reviewer comments; Updated reference

Phase chemistry in the Ca-Mn-Sb-O system at 1160-1250 °C

Phase equilibrium in the Ca-Mn-Sb-O system was studied in air at the temperature range from 1160 to 1250°C and a pseudo-quaternary phase diagram for the system CaO-MnO-Mn2O3-Sb2O5 is presented. The following compounds were discovered: new antimonate Ca 7Sb2O12 with a perovskite-like structure, solid solutions Mn2-xCaxSb2O7 (0 ≤ x ≤ 1.6) with a 3T-weberite structure, and Ca2-xMn xSb2O7 (0 ≤ x ≤ 0.23) with a 2O-weberite structure, as well as solid solutions Ca2Mn1+xSb 1-xO6 with monoclinic (0 ≤ x ≤ 0.67) and orthorhombic (0.75 ≤ x ≤ 1) perovskite structures. The existence of a number of double and ternary oxides and solid solutions on the basis of Sb 5+ and Mn2+, Mn3+, Mn4+ and with mixed manganese valence is confirmed. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

Professionally-Oriented Foreign Language Teaching of Master’s Degree Students

The issue of professionally-oriented foreign language teaching is relevant for foreign language teachers and for future professionals whose work lies in the field of intercultural communication. Foreign language skills become one of the essential requirements for technical professionals. One can determine the efficiency of the educational process by the educational tools and materials. An urgent task is to develop the standards for foreign language teaching of master’s degree students of engineering specialties. There are typical situations that arise in professional communication in the process of creating a teaching program. Professionals’ requirements regarding speech are taken into account. The method of projects in teaching allows master’s degree students to show independence in planning, organizing, controlling their activities, studying practical problems of modern age by means of a foreign language in the real information space. Designing the teaching program based on new educational standards imposes new requirements on assessing relevant competencies in master’s degree students. Individual work as an integral element of the educational process contributes to the improvement of professional qualifications

Assignment of the crystal structure to the aza-pinacol coupling product by X-ray diffraction and density functional theory modeling

Aza-pinacol coupling of N-benzyl-1-phenylmethanimine using Zn dust affords a mixture of R,S- or R,R-diastereomers in a 1:1 ratio. The R,S-diastereomer is solid with an m.p. of 135 °C, while the R,R-diastereomer is liquid at room temperature. The configuration of stereocenters was determined by combining X-ray powder diffraction and density functional theory (DFT) modeling

Thermobaric synthesis, structure, and properties of Dy x Cu 3V4O12

The perovskite-like compound Dy x Cu3V 4O12 (x = 0.67-0.75) is synthesized under high pressure (P = 4.0-9.0 GPa) and temperature (T = 1000 C). Its crystal structure is determined (Im-3 space group, Z = 2, a = 7.29348(7) Å) by means of powder X-ray diffraction. The basic lengths and bond angles are defined. It is found that the high-pressure phase of Dy x Cu3V 4O12 is characterized by metallic conductivity and paramagnetic properties. © 2013 Allerton Press, Inc

Evidence of s-wave pairing symmetry in layered superconductor Li0.68_{0.68}NbO2_2 from the specific heat measurement

A high quality superconducting Li$_{0.68}$NbO$_2$ polycrystalline sample was synthesized by deintercalation of Li ions from Li$_{0.93}$NbO$_2$. The field dependent resistivity and specific heat were measured down to 0.5 K. The upper critical field $H_{c2} (T)$ is deduced from the resistivity data and $H_{c2}(0)$ is estimated to be $\sim 2.98$ T. A notable specific heat jump is observed at the superconducting transition temperature $T_c \sim 5.0$ K at zero field. Below $T_c$, the electronic specific heat shows a thermal activated behavior and agrees well with the theoretical result of the BCS s-wave superconductors. It indicates that the superconducting pairing in Li$_{0.68}$NbO$_2$ has s-wave symmetry.Comment: 4 pages, 5 figure

Synthesis and crystal structure of a new hexagonal perovskite 7H-Ba7Li1.75Mn3.5O15.75 with Mn4+/Mn5+ charge distribution.

Our work describes the synthesis and crystal structure of a new hexagonal perovskite 7H-Ba7Li1.75Mn3.5O15.75with Mn4+/Mn5+charge distribution.</p

Correction: Synthesis and crystal structure of a new hexagonal perovskite 7H-Ba7Li1.75Mn3.5O15.75 with Mn4+/Mn5+ charge distribution.

The authors regret a spelling mistake in the surname of one of authors. The surname given as ‘Vasilev’ should be ‘Vasiliev’. Furthermore a second affiliation for the author A. D. Vasiliev was inadvertently omitted. The correct spelling and affiliations of all the authors for this paper is as shown above. The Royal Society of Chemistry apologises for these errors and any consequent inconvenience to authors and readers

Synthesis and characterization of the new high pressure phases A Cu 3 v 4O 12 (A =Gd, Tb, Er)

New ACu3V4O12 (A=Gd, Tb, Er) phases have been prepared at high pressure and high-temperature conditions (P∼8-9 GPa, T∼1000°C) in a toroid-type high pressure cell. These compounds crystallize in the cubic symmetry with a perovskite-like structure. At ambient pressure, they are paramagnetic and have activation-type conductivity. The effect of high pressure (10-50 GPa) on the electrical properties of the materials was analyzed in the temperature range from 78 to 300 K. Pressure ranges of the transition from activation type to metallic conductivity have been determined. The crystal structure of ACu3V4O12 (A=Gd, Tb, Er) was found to be stable up to 50 GPa. © 2013 Copyright Taylor and Francis Group, LLC