title: Configurational electronic entropy and the phase diagram of mixed-valence oxides: the case of LixFePO4.
abstract: We demonstrate that configurational electronic entropy, previously neglected, in ab initio thermodynamics of materials can qualitatively modify the finite-temperature phase stability of mixed-valence oxides. While transformations from low-T ordered or immiscible states are almost always driven by configurational disorder (i.e., random occupation of lattice sites by multiple species), in FePO4-LiFePO4 the formation of a solid solution is almost entirely driven by electronic rather than ionic configurational entropy. We argue that such an electronic entropic mechanism may be relevant to most other mixed-valence systems.
authors.affiliation: Department of Physics, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA.
authors.forename: Fei
authors.initials: F
authors.lastname: Zhou
authors.forename: Thomas
authors.initials: T
authors.lastname: Maxisch
authors.forename: Gerbrand
authors.initials: G
authors.lastname: Ceder