Martin Hartweg

Raman scattering on superconducting crystals of Bi2(Sr1−xCax)n+2Cun+10(6+2n)+δ (n = 0, 1)

Abstract We report Raman spectra of highly oriented crystals of Bi2Sr2CuO6+δ and Bi2Sr2CaCu2O8+δ. A factor group analysis of the k = 0 phonons is also given. Most phonons observed have Ag symmetry. A mode of B1g symmetry is observed at 282 cm−1 which is equivalent to the 337 cm−1 mode of YBa2Cu3O7.

On the structure and some properties of novel ternary pnictides: Na2M3Y4 (M = Sr, Eu; Y = P, As)

Abstract Novel ternary pnictides Na2M3Y4 (M = Sr, Eu; Y = P, As) have been prepared from binary pnictides (Na3Y and MY) and the element Y. The compounds are isotypic to Gd5Si4 (Pearson code oP 36) as revealed by single crystal X-ray diffraction (Pnma (No. 62); Na2Sr3P4: a = 735.2(2) pm, b = 1525.0(3) pm, c = 797.9(2) pm; Na2Eu3P4: a = 729.8(2) pm, b = 1504.3(3) pm, c = 788.1(1) pm; Na2Eu3As4: a = 745.9(2) pm, b = 1542.1(4) pm, c = 813.2(2) pm). These pnictides are Zintl phases containing M2+ and Na+ cations and Y4−2 dumbbells with d (PP) = 228.5 and 226.8 pm and d ( AspAs ) = 249.1 pm . The study of magnetic susceptibility and specific heat shows that Na2Eu3As4 undergoes an antiferromagnetic phase transition at 5.38 K and a predominately ferromagnetic transition at 15.2 K.

Crystal structure of potassium catena-di-μ-arsenido niccolate, K2(NiAs2)

Source of material: Title compound was prepared from a stoichiometric mixture of the elements in an evacuated and sealed silica tube at 950 K. A crucible of A1203 was used to avoid reaction with the silica ampoule. The Ni atoms are square planar coordinated by four Ρ atoms. Each Ρ atom has one Ρ and two Ni neighbours within the infinite [NiP2]~ chain. The bond lengths d(Ni-P) and d(P-P) are: 2.265(2) Ä and 2.187(4) A, respectively·

[Al2P4]6-, [Al2As4]6-, [Ga2P4]6- und [Ga2As4]6-, Zintl-Anionen mit 1,3-Dimethylencyclobutan-Struktur / [Al2P4]6-, [Al2As4]6-, [Ga2P4]6- and [Ga2As4]6-, Zintl Anions with 1.3-Dimethylene-cyclobutane Structure

The compounds Cs6M2X4 (M = Al, Ga; X = P, As) were synthesized from stoichiometric mixtures of Cs, M and Cs4X6 in sealed Nb ampoules at 950 K. They are isotypic and crystallize in the monoclinic space group P21/c (No. 14) with Z = 4 formula units per unit cell. The anion partial structure is characterized by isolated [M2X4]6- units with relatively short distances for the terminal d(M–X) bonds corresponding to a Pauling Bond Order PBO = 1.5. The distances d(M–X) of the four-membered M2X2 rings correspond to single bonds. The FIR spectra have been interpreted on the basis of the [M2X4]6- units with 2/m 2/m 2/m-D2h, symmetry by considering a factor group splitting. The assignment of the observed frequencies is supported by a normal coordinate analysis.