| Popis: |
The crystal structure of Li4[(UO2)2(W2O10)] (1) has been solved by direct methods and refined to R 1 0.036. The compound is orthorhombic, Cmc21, a = 7.3823(3), b = 14.0498(5), c = 10.1887(3) Å, V = 1056.77(7) Å3. The structure is based upon uranyl tungstate sheets with the composition [(UO2)2(W2O10)]4–. The sheets are strongly corrugated and are parallel to the (001) plane. The sheet can be described as consisting of two types of chains. UO7 pentagonal bipyramids share edges to form UO5 chains, whereas WO6 octahedra share corners to form WO5 chains. Both chains extend along the a axis. The Li+ cations reside in between the sheets providing their linkage into a three-dimensional structure. The structure can be considered as a derivative of complex oxides observed in the U—W—O and U—Mo—W—O systems. However, the topology of polyhedral linkage is different as a result of the presence of Li+ cations in the structure. The crystal chemistry of Li uranyl tungstates is discussed. |
