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A Synergistic Approach to Unraveling the Thermodynamic Stability of Binary and Ternary Chevrel Phase Sulfides
journal contribution
posted on 2020-08-12, 20:11 authored by Kristina Lilova, Joseph T. Perryman, Nicholas R. Singstock, Mykola Abramchuk, Tamilarasan Subramani, Andy Lam, Ray Yoo, Jessica C. Ortiz-Rodríguez, Charles B. Musgrave, Alexandra Navrotsky, Jesús M. VelázquezState-of-the-art
high temperature oxide melt solution calorimetry
and density functional theory were employed to produce the first systematic
study of thermodynamic stability in a series of binary and ternary
Chevrel phases. Rapid microwave-assisted solid-state heating methods
facilitated the nucleation of pure-phase polycrystalline MyMo6S8 (M = Fe, Ni, Cu; y = 0, 1, 2) Chevrel phases, and a stability trend was observed
wherein intercalation of My species engenders
stability that depends on both the electropositivity and ionic radii
of the intercalant species. Ab initio calculations
indicate that this stability trend results from competing ionic and
covalent contributions, where transition metal intercalation stabilizes
the Chevrel structure through increased ionicity but destabilizes
the structure through reduced covalency of the Mo6S8 clusters. Our calculations predicted that over intercalation
of high-valent My species leads to slight
destabilization of the Mo6 octahedral cores, which we confirm
using calorimetry and X-ray absorption spectroscopy. Our combined
computational and calorimetric analysis reveals the interplay of the
foundational principles of ionic and covalent bonding characteristics
that govern the thermodynamic stability of Chevrel and other inorganic
phases.
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Keywords
temperature oxideRapid microwave-assistedtransition metal intercalationintercalant speciesstability trend resultsSynergistic Approachstability trendsolution calorimetryheating methodsMo 6 octahedral coresMo 6 S 8 clusterscovalent contributionsThermodynamic Stabilityhigh-valent M y speciesAb initio calculationsfoundational principlesX-ray absorption spectroscopyTernary Chevrel Phase Sulfides Stat...ternary Chevrel phasesM y Mo 6 S 8M y speciesChevrel structure
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