1. Prediction of structure and cation ordering in an ordered normal-inverse double spinel
- Author
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Vancho Kocevski, Blas P. Uberuaga, Cortney R. Kreller, James A. Valdez, and Ghanshyam Pilania
- Subjects
Diffraction ,Materials science ,Monte Carlo method ,Spinel ,Thermodynamics ,Inverse ,02 engineering and technology ,Electronic structure ,engineering.material ,010402 general chemistry ,021001 nanoscience & nanotechnology ,01 natural sciences ,0104 chemical sciences ,Condensed Matter::Materials Science ,Mechanics of Materials ,engineering ,lcsh:TA401-492 ,First principle ,General Materials Science ,Condensed Matter::Strongly Correlated Electrons ,lcsh:Materials of engineering and construction. Mechanics of materials ,0210 nano-technology ,Solid solution ,Cluster expansion - Abstract
Spinels represent an important class of technologically relevant materials, used in diverse applications ranging from dielectrics, sensors and energy materials. While solid solutions combining two “single spinels” have been explored in a number of past studies, no ordered “double” spinels have been reported. Based on our first principles computations, here we predict the existence of such a double spinel compound MgAlGaO4, formed by an equimolar mixing of MgAl2O4 normal and MgGa2O4 inverse spinels. After studying the details of its atomic and electronic structure, we use a cluster expansion based effective Hamiltonian approach with Monte Carlo simulations to study the thermodynamic behavior and cation distribution as a function of temperature. Our simulations provide strong evidence for short-ranged cation order in the double spinel structure, even at significantly elevated temperatures. Finally, an attempt was made to synthesize the predicted double spinel compound. Energy Dispersive X-ray Spectrometry and X-ray diffraction Rietveld refinements were performed to characterize the single-phase chemical composition and local configurational environments, which showed a favorable agreement with the theoretical predictions. These findings suggest that a much larger number of compounds can potentially be realized within this chemical space, opening new avenues for the design of spinel-structured materials with tailored functionality. Materials with a spinel structure are used in various applications, including in the nuclear industry and as dielectrics. Here, first principle calculations and Monte Carlo simulations predict that an ordered double spinel structure is stable, supported by preliminary experimental data.
- Published
- 2020