Information-based parameters of structural complexity for two polymorphs of Ca[(UO2)2(SiO3OH)2] · 5H2O, uranophane and uranophane-β, were calculated in order to assess the impact of the structural complexity on their stability and formation. Calculations proved that uranophane-β is far more complex (IG,total = 691.90 bits/cell) than uranophane (IG,total = 345.95 bits/cell), which indirectly suggests that uranophane may form as a metastable phase during crystallization process. This suggestion is further supported by the lower density of uranophane (3.834 g/cm3) compared to that of uranophane-β (3.983 g/cm3). The hypothesis of a metastable character of uranophane is in agreement with Goldsmith's simplexity principle and the Ostwald–Volmer rule and is well supported by the frequency of occurrences of both dimorphic minerals in Nature.
Research Article|March 01, 2018
Structural complexity of uranophane and uranophane-β: implications for their formation and occurrence
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Jakub Plášil; Structural complexity of uranophane and uranophane-β: implications for their formation and occurrence. European Journal of Mineralogy ; 30 (2): 253–257. doi: https://doi.org/10.1127/ejm/2017/0029-2691
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