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Discovery of Elusive K 4 O 6 , a Compound Stabilized by Configurational Entropy of Polarons
Author(s) -
Freysoldt Christoph,
Merz Patrick,
Schmidt Marcus,
Mohitkar Shrikant,
Felser Claudia,
Neugebauer Jörg,
Jansen Martin
Publication year - 2019
Publication title -
angewandte chemie international edition
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 5.831
H-Index - 550
eISSN - 1521-3773
pISSN - 1433-7851
DOI - 10.1002/anie.201809409
Subject(s) - polaron , configuration entropy , thermodynamics , entropy (arrow of time) , endothermic process , thermalisation , statistical physics , exothermic reaction , electron , chemical physics , solid state , materials science , chemistry , physics , adsorption , quantum mechanics
Synthesis of elusive K 4 O 6 has disclosed implications of crucial relevance for new solid materials discovery. K 4 O 6 forms in equilibrium from K 2 O 2 and KO 2 , in an all‐solid state, endothermic reaction at elevated temperature, undergoing back reaction upon cooling to ambient conditions. This tells that the compound is stabilized by entropy alone. Analyzing possible entropic contributions reveals that the configurational entropy of “localized” electrons, i.e., of polaronic quasi‐particles, provides the essential contribution to the stabilization. We corroborate this assumption by measuring the relevant heats of transformation and tracking the origin of entropy of formation computationally. These findings challenge current experimental and computational approaches towards exploring chemical systems for new materials by searching the potential energy landscape: one would fail in detecting candidates that are crucially stabilized by the configurational entropy of localized polarons.