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Geometric magnetic frustration arises when the geometry of a structure prevents the simultaneous fulfillment of nearest-neighbor antiferromagnetic interactions and is commonly observed in lattices that exhibit a triangular topology, such as those found in the pyrochlore structure. Via a mild hydrothermal route, we have synthesized seven quaternary β-pyrochlore related fluorides AxM2+xM3+(2–x)F6, (A = Cs and Rb; M2+ = Co2+, Ni2+ and Zn2+; and M3+ = V3+ and Fe3+). Crystal structures and compositions were determined using a combination of single-crystal X-ray diffraction and energy-dispersive spectroscopy. After adjusting the reaction conditions, phase pure products of AxM2+xM3+(2–x)F6 were obtained. The magnetic susceptibility and isothermal magnetization data for all seven compounds were collected to interpret the magnetic behavior, which ranged from paramagnetic to antiferromagnetic with and without a ferromagnetic component. We found that the magnetic behavior of the AxM2+xV3+(2–x)F6 pyrochlore structures strongly depends on the presence or absence of unpaired electrons on the M2+ position. The titled pyrochlore compounds, with the exception of the Zn-analog, can be considered frustrated materials, with frustration indices in the range of 6 –13. 

Single crystals of A₃MF₆(A = Rb, Cs; M = Al, Ga) were grown from mixed alkali chloride/fluoride fluxes. The polymorphism of each compound was studiedviaTGA/DSC and high temperature X-ray diffraction.

 

Few plutonium containing silicates have been reported in the literature and only one other tetravalent plutonium silicate structure has been reported using the flux growth method. With the goal of understanding actinide incorporation into silicates, we describe herein two new plutonium (IV) silicates, Rb₂PuSi₆O₁₅and K₂PuSi₂O₇, synthesized using a mixed alkali chloride/alkali fluoride flux growth. Both structures crystallize in theC2/cspace group with lattice parametersa=24.2980(10) Å,b=7.1466(3) Å,c=17.2025(8) Å and =96.6560(10)° for Rb₂PuSi₆O₁₅, anda=9.9478(2) Å,b=5.59820 (10) Å,c=13.1848(2) Å, and =105.7400(10)° for K₂PuSi₂O₇. Comparisons to the synthesis of other reported alkali actinide silicates (Ce, U, and Th) are made. Raman spectra and DFT calculations of formation enthalpies and vibrational modes provide confirmation of structure refinements and enhanced product characterization for comparison with other materials.

 

Oxidation states (OS) are the charges on atoms due to electrons gained or lost upon applying an ionic approximation to their bonds. As a fundamental property, OS has been widely used in charge‐neutrality verification, crystal structure determination, and reaction estimation. Currently, only heuristic rules exist for guessing the oxidation states of a given compound with many exceptions. Recent work has developed machine learning models based on heuristic structural features for predicting the oxidation states of metal ions. However, composition‐based oxidation state prediction still remains elusive so far, which has significant implications for the discovery of new materials for which the structures have not been determined. This work proposes a novel deep learning‐based BERT transformer language model BERTOS for predicting the oxidation states for all elements of inorganic compounds given only their chemical composition. This model achieves 96.82% accuracy for all‐element oxidation states prediction benchmarked on the cleaned ICSD dataset and achieves 97.61% accuracy for oxide materials. It is also demonstrated how it can be used to conduct large‐scale screening of hypothetical material compositions for materials discovery.