Thermal Phase Transition of Cesium Formate

Article abstract of DOI:10.1021/ic00116a002

The phase transition of cesium formate observed at around 36°C was found to be a reversible first-order transition by means of thermal analyses. The results of the Rietveld analysis of powder X-ray diffraction data showed that an orthorhombic phase (Pbcm, Z = 8; a = 4.785(1), b =9.553(9), and c = 15.927(2) ?) transformed to a cubic phase (Pm3m, Z = 1; a = 4.500(5) ?). The large values of enthalpy and entropy change for the transition (ΔHtr = 6.87 .+-. 0.28 kJ mol**-1 and ΔStr = 22.2 .+-. 0.9 J K**-1 mol**-1) were discussed on the basis of the change of the orientation freedom of the formate ion.