Mössbauer analysis and modeling of the order-disorder localization-delocalization transition in the mixed-valence salt diethyl biferrocenium tri-iodide

Abstract
The thermal behavior of diethyl biferrocenium tri-iodide has been reinvestigated with further detail in the range 250–300 K by Mössbauer spectroscopy. The data strongly suggests the onset of a localized-delocalized second-order transition, and are successfully reproduced by a cooperative adaptation of the vibronic Piepho-Krausz-Schatz model. The shape and amplitude of the expected contribution to the specific heat are discussed, as well as other spectroscopic data. DOI: http://dx.doi.org/10.1103/PhysRevB.47.14070 © 1993 The American Physical Society