Phase sequence in diisopropylammonium iodide: avoided ferroelectricity by the appearance of a reconstructed phase

Crystals of diisopropylammonium iodide are synthesized, grown and characterized. Two phases: P21/m (Z = 1) and P212121 (Z = 2) are observed. In contrast with analogous compounds no polar phase occurs, despite a critical-like electric behaviour. A phenomenological theory is proposed to describe the thermodynamics of the whole family of diisopropylammonium halides