Structural studies of (TMTSF)₂SbCl₂F₄, α-(BEDT-TTF)₂I₃ and some organic superconductors found recently

X-ray studies were made of structural changes in the organic conductors (TMTSF)₂SbCl₂F₄ and α-(BEDT-TTF)₂I₃. The former material undergoes an orientational ordering of the non-centrosymmetric anion SbCl₂F₄ at about 160 K. In the latter material the molecular dimerization occurs at 135 K. These structural changes are discussed in relation to metal - insulator transitions taking place at the above temperatures. X-ray diffraction and scattering studies were also made on the recently found organic superconductors (DMET)₂X [X = Au(CN)₂ and Aul₂] and (BEDT-TTF)₂Cu(SCN)₂, the latter of which becomes superconducting at about 10 K, the highest temperature ever reported. No structural anomaly was found in these materials, suggesting that the metal - insulator transition of the former material at ambient pressure is driven by an onset of the SDW state.