MS15-P04 Evolution of uranyl-bearing structural complexes Vladislav Gurzhiy (St. Petersburg State University, Crystallography Dept., St. Petersburg, Russia) Sergey Krivovichev (St. Petersburg State University, Crystallography Dept., St. Petersburg, Russia)email: vladgeo17@mail.ruUranyl sulfates and selenates are the most remarkable groups of U6+-containing compounds due to their mineralogical importance and fascinating variety of structural topologies and topological isomers. The unique diversity of these materials can be explained by the high topological and structural adaptability of uranyl-based structural units to the charge and shape of organic and/or inorganic complexes that compensate for the negative charge of the uranyl complexes. Due to the small energetic differences between distinct topologies with the same overall composition, the structures of uranyl-based units may adapt to a particular template through topological and geometrical variations, thus demonstrating considerable structural flexibility. The interesting problem that appears in this regard is how complexity of a particular topological structure is related to the shape and complexity of templating ions.
Within the conceptual framework of the information-based approach, uranyl-containing 1D and 2D units have been investigated using topological approach and information-based complexity measures demonstrating that very complex structures may form as transitional architectures between phases with relatively small amounts of structural information [1], wherein the overall trend shows that complexities of structures formed on the latter stages of crystallization are higher than those for the phases growing on the primary stages [2]. In addition, it was found that complex topologies form more rare than their simplest counterparts, which is a response of the crystal structure to changes of chemical conditions within the system [3].
This work was supported by St. Petersburg State University, President of Russian Federation grant for young scientists (no. MK-4810.2018.5) and Russian Science Foundation (no. 18-17-00018).

[1] Gurzhiy, V.V., Tyumentseva, O.S., Krivovichev, S.V., Krivovichev, V.G., Tananaev I.G. (2016) Cryst. Growth Des., 16, 4482-4492.

[2] Gurzhiy, V.V., Krivovichev, S.V., Tananaev I.G. (2017) J. Solid State Chem., 247, 105-112.

[3] Gurzhiy, V.V., Tyumentseva, O.S., Krivovichev, S.V., Tananaev I.G. (2018) Z. Kristallogr. 233, 233-245.
Keywords: Uranyl, crystal structure, structural complexity