A simple approach for determination of the phase transition temperature using infrared temperature-induced isosbestic points.

The appearance and formation of an isosbestic point in the temperature-dependent IR spectra can be used to reveal a phase transition at a certain temperature. This conclusion was made by a thorough investigation of the IR (transmission and ATR) spectra of methylammonium iodide (MAI) and formamidinium iodide (FAI) recorded in a wide temperature range starting from -170 to +200 °C. By investigating the isosbestic points, it was found that MAI undergoes two phase transitions at -110 and +146 °C.

Classification of perovskites with supervised self-organizing maps.

In this work supervised self-organizing maps were used for structural classification of perovskites. For this purpose, structural data for total number of 286 perovskites, belonging to ABO3 and/or A2BB'O6 types, were collected from literature: 130 of these are cubic, 85 orthorhombic and 71 monoclinic. For classification purposes, the effective ionic radii of the cations, electronegativities of the cations in B-position, as well as, the oxidation states of these cations, were used as input variables.