Novel structural modulation in the ambient-pressure sulfur-based organic superconductor .beta.-(BEDT-TTF)2I3: origin and effects on its electrical conductivity

The description and analysis of composite crystals

“…The I atoms show large translational and rotational rigid-bod~, displacements, with amplitudes of up to 0.12 A and 6.7 °, respectively. Similar large displacements of the I3 ions were observed in the modulated structure of (ET)213 (Leung, Emge, Beno, Wang, Williams, Petricek & Coppens, 1985).…”

Effective Coulomb interactions within BEDT-TTF dimers

“…47 Nuclear positions for C and S atoms were obtained from x-ray crystallography. 24,25,[48][49][50][51][52][53] H atoms, which are not observed in x-ray scattering experiments, were relaxed by the conjugate-gradient method. Total DFT energy differences between the relevant charge states ͓E͑1͒ − E͑0͔͒ and ͓E͑2͒ − E͑0͔͒ were equated with the corresponding analytical expressions in Eq.…”

“…where c is the interlayer lattice constant taken from the relevant x-ray scattering measurements 48,51 and t Ќ is the interlayer hopping integral, which has previously been estimated from experimental data for both -͑ET͒ 2 Cu͓N͑CN͒ 2 ͔Br ͑Ref. 64͒ and ␤-͑ET͒ 2 I 3 ͑Ref.…”

Raman-Studies of the Organic Superconductor β-(BEDT-TTF)2IAuI

“…Even very small changes can seriously influence the superconducting transition. In the organic charge transfer-salt /?-(BEDT-TTF) 2 I 3 [BEDT-TTF = bis-(ethylenedithio)tetrathiofulvalene] below 195 K exists an incommensurate modulation [1] and below 125 K a commensurate superstructure with a pronounced distortion of the Ijanions [2], Under ambient pressure the superconducting transition temperature T c is 1.3 K [3] but after a particular pressure-temperature cycling procedure superconductivity can be stabilized at ambient pressure even at r c =8.1 K [4], A recent neutron diffraction study has shown that the high-r c superconducting phase of /?-(BEDT-TTF) 2 I 3 is completely ordered [5] showing that during the pressure-temperature cycling procedure the distortion of the Ij-anions in /?-(BEDT-TTF) 2 I 3 is suppressed resulting in an increase of T c . The IJ-anions and other polyhalide ions used in organic superconductors are sensitive to distortions and slight changes in the crystal.…”