A Systematic Study Of The Relationship Between Crystal Structurem, ESR Characteristics And Electerical Properties In Bedt-TTF Synthetic Metals

The crystal packing motifs exhibited by the BEDT-TTF (or “ET”) donor molecules in the various ET:X charge-transfer salts are summarized. In spite of the variable stoichiometries and crystall symmetries found for these synthetic metals, the number of different cyrstal packing motifs is limited — two interstack (L- and Z-modes) and three intrastack modes (a-, ab- and c- modes). Of these superconductivity has been observed only i the 2:1 (BEDT-TTF:X) salts which adopt a combination of the L- and a- modes of inter-and intrastack paking, respectibvely, ESR linewidth measurement provide a maans of separating different crystal phases within a given donoracceptor system and are especially useful in differentiating the non-superconducting a-(ET) 2× phases, x=13- and IBrz-, form the abient pressure superconduction g β-(ET)2x phases, x=I3 - IBrz- (TC;s = 1. 4 K and 2. 7 K. respectibely).