Franz Rau

β-PtO2: High pressure synthesis of single crystals and structure refinement

Abstract Single crystals of β-PtO2 have been grown from PtKC103-mixtures at 40 kbar, 1500 °C in a modified Belt-type apparatus using Pt-capsules. The crystals are orthorhombic, space group Pnnm, with a=4.4839(3) A, b=4.5385(6) A, c=3.1360(6) A and Z=2. Single crystal X-ray data confirmed the structure to be CaCl2-type, a distorted variant of the rutile structure. The PtO distances are 2 × 1.989(4) and 4 × 2.003(4) A, the shortest oxygenoxygen distance is 2.494(5) A. A discussion of some geometrical features is presented.

High pressure synthesis of Cu2GeO4 with hausmannite structure

Copper(II)metagermanate, CuGeO3, decomposes at high pressure to rutile-type GeO2 and Cu2GeO4. Very small single crystals of Cu2GeO4 can be obtained by direct high pressure synthesis from CuOGeO2 mixtures. The compound has a distorted spinel structure (Hausmannite structure, space group I41amd) with a = 5.593 A, c = 9.396 A, Z = 4.

Studies on AB2-type intermetallic compounds, IV. High-pressure synthesis and crystal structure of scandium dizinc ScZn2

Abstract Single crystals of the hitherto unknown intermetallic compound ScZn2 could be obtained from the elements by high-pressure high-temperature reaction in a modified Belt-type apparatus (h-BN capsule, 40 kbar, 1900 → 1200 → 25 °C, and subsequent release of high pressure). The crystals are hexagonal, space group P6, Imma, with a = 5.2509(8), c = 8.4774(14) A , c a = 1.6147 and Z = 4. Final residuals after refinement against F2 were R1 = 0.0349, wR2 = 0.0752 and S = 1.117 for 11 parameters and all 86 unique data. ScZn2 is a Laves-Friauf phase adopting the C14 (MgZn2) type.

KMo4O6 revisited evidence for Mo6 cluster-centering interstitial atoms in the high-pressure phase KMo4O6-II

Abstract The c -axis lengths of various “KMo 4 O 6 ” samples, prepared by high-temperature, high-pressure decomposition of K 2 MoO 4 , vary in the range from 2.908 to 2.943 A, all of them being larger than the corresponding c -axis for KMo 4 O 6 prepared by electrolysis of K 2 MoO 4 /MoO 3 melts ( c = 2.879 A). From a single-crystal structure refinement of a crystal with c = 2.917 A we gained evidence that the different lengths of the c -axes in the high-pressure phases KMo 4 O 6 -II are caused by additional atoms which center otherwise empty Mo 6 octahedra. Assuming these interstitial atoms to be oxygens, the results of bond valence and bond order sum calculations are clearly improved. The influence of different synthetic routes to KMo 4 O 6 , as well as some peculiarities observed during the structure refinement for KMo 4 O 6 samples of different origin, are discussed.

Gold-Alkalimetallsysteme, III. Hochdrucksynthese und Kristallstruktur von Rb3Au7 [1] / Gold-Alkali Metal-Systems, III. High Pressure Synthesis and Crystal Structure of Rb3Au7 [1]

Abstract The intermetallic compound Rb3Au7 could be synthesized from the elements at 4 kbar, 700 °C in a modified Belt-type apparatus. The structure (Cmmm; a = 5.579(1), b = 13.267(5), c = 7.265(2) Å; Z = 2; R = 0.035, Rw = 0,031) comprises three crystallographically independent Au atoms, arranged in layers along the c-axis. The shortest interatomic distances are Au -Au = 2.633Å, Au -Rb = 3.438Å and Rb -Rb = 3.622Å.

Hochdrucksynthese und Strukturverfeinerung von SrVO3, Sr2VO4 und Sr3V2O7 / High-Pressure Synthesis and Structure Refinement of SrVO3, Sr2VO4, and Sr3V2O7

Single crystals of SrVO3, Sr2VO4 and Sr3V2O7 have been obtained by high-pressure reactions in a modified belt-type apparatus. The crystal structures, refined from diffractometer data, are as follows: SrVO3, perovskite type, Pm3̄m, a = 3.8408(3) Å, R = 0.017, Rw = 0.018, composition from occupancy refinement of oxygen positions SrVO2.93(2); Sr2VO4, K2NiF4 type, I 4/mmm, a = 3.837(1), c = 12.569(1) Å, R = 0.014, Rw = 0.017; Sr3V2O7, Sr3Ti2O7 type, I 4/mmm, a = 3.839(1), c = 20.262(2) Å, R = 0.020, Rw = 0.029.

Hochdrucksynthese und Kristallstruktur von Kalium- und Rubidiumdiwolframat(VI), K2W2O7 und Rb2W2O7 / High-Pressure Synthesis and Crystal Structure of Potassium and Rubidium Ditungstate(VI), K2W2O7 und Rb2W2O7

Potassium tungstate, K2WO4, decomposes at high pressures to give K2W2O7 and other products. Single crystals of K2W2O7 could be synthesized from a mixture of K2WO4 + WO3 at 40kbar, 1000 °C. The crystals are monoclinic, space group P21/c, with a = 3.883(1) A, b = 13.653(4) Å, c = 5.960(1) Å, β = 90.40(3)°, and Ζ = 2. The structure is comprise of distorted WO6-octahedra (W–O = 1.75-2.13 A) which are connected by corner- and edgesharing, thus forming layers with a sequence ABAB ... along [010]. The potassium ions are situated between the layers with K–O distances of 2.66-3.04 A. Rb2W2O7, synthesized from a Rb2WO4/WO3-mixture at 40 kbar, 1000 °C, is isostructural with K2W2O7 (a = 3.9645(4) Å, b = 14.119(1) Å, c = 6.0415(5) Å,β = 90.446(9)°.