#beta#_(co)-(ET)_2I_3: Co-existence of ordered #beta#-(ET)_2I_3 (T_c ≈ 8 K) and disordered #beta#-(ET)_2I_3 (T_c ≈ 2 K)

摘要

The crystal structures of #beta#_(co)-(ET)_2I_3 were determined at temperatures of 293, 200, 130, 100, and 35 K from X-ray single crystal diffraction data. At 293 K, one ethylene group of the ET cations is disordered with the eclipsed conformation prevailing over the staggered conformer; at 200 K the occupancies of both arrangements are equal. Upon cooling to 130 K and below, about 60 percent of the ethylene groups adopt a staggered conformation, thus providing evidence for a temperature-induced, partial ordering process.