An alteration of the uranyl oxide hydroxy-hydrate mineral schoepite [(UO₂)₈O₂(OH)₁₂](H₂O)₁₂ at mild hydrothermal conditions was studied. As the result, four different crystalline phases Cs[(UO₂)(SO₄)(OH)](H₂O)_0.25 (1), Cs₃[(UO₂)₄(SO₄)₂O₃(OH)](H₂O)₃ (2), Cs₆[(UO₂)₂(SO₄)₅](H₂O)₃ (3), and Cs₂[(UO₂)(SO₄)₂] (4) were obtained, including three novel compounds. The obtained Cs uranyl sulfate compounds 1, 3, and 4 were analyzed using single-crystal XRD, EDX, as well as topological analysis and information-based structural complexity measures. The crystal structure of 3 was based on the 1D complex, the topology of which was unprecedented for the structural chemistry of inorganic oxysalts. Crystal chemical analysis performed herein suggested that the majority of the uranyl sulfates minerals were grown from heated solutions, and the temperature range could be assumed from the manner of interpolyhedral linkage. The presence of edge-sharing uranyl bipyramids most likely pointed to the temperatures of higher than 100 °C. The linkage of sulfate tetrahedra with uranyl polyhedra through the common edges involved elevated temperatures but of lower values (~70–100 °C). Complexity parameters of the synthetic compounds were generally lower than that of uranyl sulfate minerals, whose structures were based on the complexes with the same or genetically similar topologies. The topological complexity of the uranyl sulfate structural units contributed the major portion to the overall complexity of the synthesized compounds, while the complexity of the respective minerals was largely governed by the interstitial structure and H-bonding system.

Six novel uranyl nitrate compounds K₃[(UO₂)(NO₃)Cl₃](NO₃) (1, 2), α-Cs₂[(UO₂)(NO₃)Cl₃] (3), [(UO₂)(NO₃)₂(H₂O)₂][(CH₃NH₃)₂(NO₃)₂] (4), Cs₂[(UO₂)(NO₃)₄] (5), and [(UO₂)₂(OH)₂(NO₃)₂(H₂O)₃](H₂O) (6) have been prepared from aqueous solutions. Their structures were analyzed using single-crystal X-ray diffraction technique. Structural studies have shown that the crystals of 1 and 2 are isotypic but differ in the distortion at the counter ion’s sites. The crystal of 3 is a low-temperature polymorph modification of the recently studied compound. The crystal structure of 4 is composed of uranyl-dinitrate-dihydrate and methylamine-nitrate electroneutral complexes linked through the system of H-bonds. The crystal structure of 5 is based on the finite [(UO₂)(NO₃)₄]²⁻ clusters that are arranged in pseudo-chained complexes extended along [100] and are arranged according to a hexagonal packing or rods. The crystal of 6 is also a novel polymorph modification of previously studied compound, the structure of which is based on the very rare topological type of the finite clusters. Nowadays, uranyl nitrate finite clusters of nine various topological types are known. We give herein a short review of their topological features and relationships. Crystallization of uranyl nitrates usually occurs when all other competitive anions in the system have already formed crystalline phases, or the reaction of reagents have slowed down or even stopped. Thus it is suggested that crystallization of uranyl nitrates can be used as a key indicator of the reaction progress, which points to the necessity of the initial concentrations of reagents correction, or to the replacement of reagents and adjustment of the thermodynamic (P,T) parameters of the synthesis.

Through the combination of low-temperature hydrothermal synthesis and room-temperature evaporation, a synthetic phase similar in composition and crystal structure to the Earth’s most complex mineral, ewingite, was obtained. The crystal structures of both natural and synthetic compounds are based on supertetrahedral uranyl-carbonate nanoclusters that are arranged according to the cubic body-centered lattice principle. The structure and composition of the uranyl carbonate nanocluster were refined using the data on synthetic material. Although the stability of natural ewingite is higher (according to visual observation and experimental studies), the synthetic phase can be regarded as a primary and/or metastable reaction product which further re-crystallizes into a more stable form under environmental conditions.