2, University of California, Santa Barbara, Santa Barbara, California, United States
3, ETH Zurich, Zurich, , Switzerland
4, Illinois Applied Research Institute, Urbana, Illinois, United States
In order to capitalize on computational modeling and predictions, fast and accurate experimental synthesis and characterization techniques must evolve. In this study, we investigate transition metal chalcogenides using high-throughput experimental techniques, such as temperature and time-resolved in-situ x-ray diffraction, powered by computational predictions. High-temperature in-situ x-ray diffraction accelerates materials discovery by allowing us to watch a chemical reaction in real time and identify new stable/metastable phases. It provides useful insights into the thermodynamics and kinetics of reactions. Transition metal chalcogenides are particularly interesting because of their understudied d-electron correlations which lead to various interesting properties including superconductivity, meta-magnetic metallic behavior, and quantum phase transitions.
I applied such a tandem approach to explore the Ba–Ru–S phase space using a combination of evolutionary algorithms and density functional theory (DFT) to inform traditional and in situ diffraction methods. My work identified a high-temperature polymorph of BaS2, that would have been otherwise missed in ex-situ reactions and did not reveal formation of the predicted candidates BaRu2S2 or BaRuS3 (Bhutani, A. et al. Chem. Mater. 29 (14), 5841–5849 (2017)). I then used this methodology to study several other ternary systems to screen for novel phases. I screened 31 ternary chalcogenide phase diagrams of the form XYZ (X = K, Na, Ba, Ca, Sr, La, K, Bi, Pb; Y is a 3d transition metal; and Z = S or Se), where DFT predicted new compositions (Wagner Research Group, Physics, UIUC). I discovered 9 new phases belonging to the K/Na-Zn-S/Se systems with potential uses as wide band gap semiconductors and found 27 phase diagrams to be “empty” in the case of bulk synthesis (Narayan, A., Bhutani, A. et al. Phys. Rev. B. 94, 045105 (2016)). I complete my study with detailed characterization of new phases using XRD, UV-Vis Spectroscopy, SEM and magnetic and transport measurements.