Hochdrucksynthesen einiger Carbonate mit überkritischem CO₂

Abstract

Die Carbonate der Alkalimetalle und einer Reihe von Übergangsmetallen lassen sich darstellen durch Einwirkung von CO2 unter Drucken zwischen 600 und 4500 at bei Temperaturen zwischen 100 und 400°C auf entsprechende Salzlösungen, Hydroxide oder Oxide. Die auf diese Weise dargestellten Verbindungen MnCO3, FeCO3, CoCO3, NiCO3, ZrOCO3 · 2H2O, Th(CO3) · 0,5 H2O sowie die Alkalimetallcarbonate werden IR‐spektroskopisch und röntgenographisch charakterisiert. Die Strukturen von Rb2CO3 (1) und Cs2CO3 (2) werden mitgeteilt: Sie kristallisieren beide in der monoklinen Raumgruppe P 2 1/c (Nr. 14) mit a = 5,87 (1) bzw. 6,13 (2), b = 10,13 (1) bzw. 10,28 (2), c = 7,33 (1) bzw. 8,15 Å (2), β = 97,65° (1) bzw. 95,85° (2) mit Z = 4.

Crystal Structures and Topological Aspects of the High‐Temperature Phases and Decomposition Products of the Alkali‐Metal Oxalates M2[C2O4] (M=K, Rb, Cs)

“…Refinement of the crystal structure of the room temperature modification of g-Rb 2 [CO 3 ] (and isostructural g-Cs 2 [CO 3 ] confirmed the literature data. [22] The differences between the g-, b-, and a-phases for potassium, rubidium, and cesium carbonate are mainly due to the different orientations of the rigid carbonate ion: whereas in the g-modification the carbonate ions are inclined around two axes with respect to each other, they are inclined around only one axis in the b-phase because of an additional mirror plane running through the CO 3 2À ions. Therefore, no disorder model is necessary to match the powder-diffraction pattern of the b-modification.…”

Tl2CO3at 3.56 GPa

“…The shortest CÁ Á ÁC distance in Tl 2 CO 3 at ambient pressure is 3.46 Å (Marchand et al, 1975), comparable with values observed in other M 2 CO 3 carbonates, viz. 3.16 Å in Li 2 CO 3 (Effenberg & Zemann, 1979) or up to 4 Å for Cs 2 CO 3 (Ehrhardt et al, 1980). In the high-pressure form of Li 2 CO 3 at 10 GPa this distance decreases to 2.57 Å (Grzechnik et al, 2003;Cancarevic et al, 2006).…”

Series of Crystals with Giant Optical Anisotropy: A Targeted Strategic Research

“…The compounds with alkali and alkaline earth metal cations are screened in terms of the type of FMs, [CO 3 ] 2− , [C 2 O 4 ] 2− , [C 2 O 6 ] 2− , 1 [C 4 O 4 ] 2− , 2 [C 4 O 4 ] 2− , and [C 6 O 6 ] 2− . Totally, 29 selected structures [25–44] are screened with the formula A n CO 3 (A=Li, Na, K, Rb, Cs, n =2; A=Mg, Ca, Sr, Ba, n =1), A n C 2 O 4 (A=NH 4 , Li, Na, K, Rb, Cs, n =2; A=Ca, Ba, n =1), A n C 2 O 6 (A=K, Rb, n =2), A n C 4 O 4 (A=NH 4 , H, Li, Na, Rb, Cs, n =2; A=Ca, Ba, n =1), and Na 2 C 6 O 6 , as listed in Table 2.…”

“…TheC ÀOunits are obtained from primary crystal information without structure optimization. Thepolarization anisotropy was acquired from static polarization according to the following formula: [25][26][27][28][29][30][31][32][33][34][35][36][37][38][39][40][41][42][43][44] are screened with the formula [2] YVO 4 ,r utile (TiO 2 ), [45] respectively. Na 2 C 6 O 6 possesses the largest birefringence in reported crystals to the best of our knowledge.…”