Full crystal structure, hydrogen bonding and spectroscopic, mechanical and thermodynamic properties of mineral uranopilite

Abstract

The determination of the full crystal structure of the uranyl sulfate mineral uranopilite, including the positions of the H atoms in the corresponding unit cell, has not been feasible to date due to the poor quality of its X-ray diffraction pattern.

Uranoclite, a new uranyl chloride mineral from the Blue Lizard mine, San Juan County, Utah, USA

“…The bands of highest intensity in this region are centred near 1226, 1189, and include a moderately intense and complex doublet near ~1040 and 1005 cm -1 . These assignments are in line, for instance, with multiple bands observed in this range related to () U-OH, librations of H 2 O and overtones, found in the calculated spectra of uranopilite (Colmenero et al 2020). Previously, these bands were generally assigned to stretching modes of SO 4 tetrahedra.…”

Thermodynamic properties of the uranyl carbonate minerals roubaultite, fontanite, widenmannite, grimselite, čejkaite and bayleyite

“…The relative ThSs of eighteen important secondary phases of SNF were determined from the computed thermodynamic functions of the uranyl carbonate minerals obtained in this work and those reported in previous papers. 59,[66][67][68][69][70][71][72][75][76] C, respectively, in the temperature range going from 300 to 500 K. Fig. 7.A, shows that the most stable phase at H 2 O 2 -free conditions is grimselite, which is more stable than soddyite, the most stable phase found in previous works, by −791.9 kJ • mol −1 at room temperature.…”

“…[49][50] The knowledge of the crystal structures of uranyl-containing minerals is interesting itself for the investigation of the paragenetic sequence of minerals arising from the oxidative dissolution processes of uraninite in uranium ore deposits 8,10,15,19,[51][52] and spent nuclear fuel (SNF) in NWRs, 8,,11,20.40-45 and for the evaluation of the incorporation of fission products and actinides in the corresponding structures. [53][54][55][56] However, the availability of the full crystal structures of uranyl containing minerals is also relevant because opens the possibility of the safe and efficient computation of their vibrational spectra [47][48][57][58][59][60][61][62][63][64][65][66][67][68] and physicochemical properties 46,48, employing the first principles solidstate methodology. The knowledge of the optimized structures of the uranyl carbonate minerals rutherfordine, bayleyite, roubaultite, fontanite, widenmannite, grimselite and čejkaite [46][47][48] was exploited for the theoretical determination of their mechanical properties.…”

“…The lack of thermodynamic data for the uranyl carbonate minerals and the discrepancies found between some of the measured properties may be related to the difficulties encountered with attempting to control atmospheric compositions. 17 A detailed analysis of the previous theoretical studies, 59,[66][67][68][69][70][71][72][75][76] suggests that the first principles methodology is an excellent complement to experimental methodology and provides accurate temperature-dependent thermodynamic functions for uranyl-containing materials. These studies showed that there are significant variations on the relative thermodynamic stabilities (ThS) of uranium minerals as the temperature increases.…”

“…These studies showed that there are significant variations on the relative thermodynamic stabilities (ThS) of uranium minerals as the temperature increases. [71][72]68 Therefore, the necessity of temperaturedependent data to understand the thermal history of the mineral assemblages is evident. This is particularly important for the performance assessment of NWRs in which significant variations of the temperature are expected over time.…”