X-ray investigations of the low-temperature phases of the organic metals α- and β-(BEDT-TTF)2I3

Abstract

The structure of single crystals of the organic metals α- and β-(BEDT-TTF) was determined at 100 K, well below the phase transitions indicated by resistivity and thermopower measurements as well as by differential thermal analysis. In the α-phase no unusual change of the room temperature unit cell but a slight variation in the triiodide network and especially a more pronounced dimerization in one of the two donor stacks have been found. The β-phase develops a superstructure with a unit cell volume three times as large as that at room temperature and with pronounced distortions of the I3--ions.