STRUCTURE INVESTIGATIONS OF Rb2Li4(SeO4)3 *2H2O CRYSTALS. Wieslawa Bronowska1 and Adam Pietraszko2, 1Institute of Physics, Technical University of Wroclaw, Wybrzeze Wyspianskiego 27, 50-370 Wroclaw, Poland, 2Institute of Low Temperature and Structure Research, Polish Academy of Sciences, 50-950 Wroclaw, Poland
In recent years, much attention has been devoted to the two-component systems of the Li2SO4 - Me2SO4 type, where Me = Rb, Cs, K, NH4, as a consequence of the wide range of their physico-chemical properties. An interesting feature of these compounds is the existence of successive phase transitions between their different phases. In part, scientific interest in these systems is motivated by the desire to compare the structural and physical properties of these compounds and to investigate how their feature may be influenced by the structural characteristic.
This paper reports the X-ray powder and single crystal diffraction results obtained for the two-component crystals, Rb2Li4(SeO4)3 *2H2O, which belong to a new family of selenates hydrates. Crystals were obtained by evaporation of a saturated solution. These crystals have a monoclinic symmetry, (space group P21/c), with two chemical units forming the room temperature unit cell. Lattice parameters at room temperature are the following: a = 5.256(1)Å, b = 5.178(1)Å, c = 26.739(5)Å, [[beta]] = 93.11(3)deg; V= 726.6(2)Å3. The final discrepancy factor is R = 0.042 for 1272Fo > 4[[sigma]](Fo). The refinements of the crystal structure of Rb2Li4(SeO4)3 *2H2O have shown that oxygen atoms of a crystalline water statistically occupy two different positions. The presence of the water molecules in the crystal structure has been confirmed by the infrared measurements. The powder diffraction measurements were performed over the temperature range from 30K to 300K.