Similarities and differences in the structural and electronic properties of .kappa.-phase organic conducting and superconducting salts

• Published in: Inorganic chemistry Vol. 28; no. 25; pp. 4516 - 4522
• Main Authors: Jung, D, Evain, M, Novoa, J. J, Whangbo, M. H, Beno, M. A, Kini, A. M, Schultz, A. J, Williams, J. M, Nigrey, P. J
• Format: Journal Article
• Language: English
• Published: Washington, DC American Chemical Society 01.12.1989
• Subjects: 360603 - Materials- Properties; 400201 - Chemical & Physicochemical Properties; ANTITHYROID DRUGS; CARBONIC ACID DERIVATIVES; COMPLEXES; Condensed matter: electronic structure, electrical, magnetic, and optical properties; COPPER COMPLEXES; CYANIDES; DATA; DRUGS; ELECTRIC CONDUCTIVITY; ELECTRICAL PROPERTIES; Electron density of states and band structure of crystalline solids; Electron states; ELECTRONIC STRUCTURE; Exact sciences and technology; EXPERIMENTAL DATA; GOLD COMPLEXES; HORMONE ANTAGONISTS; INFORMATION; INORGANIC, ORGANIC, PHYSICAL AND ANALYTICAL CHEMISTRY; MATERIALS SCIENCE; MOLECULAR STRUCTURE; NUMERICAL DATA; ORGANIC COMPOUNDS; ORGANIC SULFUR COMPOUNDS; PHYSICAL PROPERTIES; Physics; SUPERCONDUCTIVITY; THIOCYANATES; TRANSITION ELEMENT COMPLEXES; Band structure; Superconducting materials; Metal insulator transition; Gold Complexes; Organic conductor; Fermi surface; Experimental study; Copper Complexes; Crystalline structure
• ISSN: 0020-1669; 1520-510X
• DOI: 10.1021/ic00324a018

The similarities and differences in the crystal and band electronic structures of four {kappa}-phase tetrathiafulvalene-based organic conducting salts {kappa}-(BEDT-TTF){sub 2}X (X{sup {minus}} = Cu(NCS){sub 2}{sup {minus}}, I{sub 3}{sup {minus}}), {kappa}-(MDT-TTF){sub 2}AuI{sub 2}, and {kappa}-(BMDT-TTF){sub 2}AU(CN){sub 2} have been examined. Donor dimers have a bond-over-ring arrangement in the superconducting salts {kappa}-(BEDT-TTF){sub 2}X (X{sup {minus}} = Cu(NCS){sub 2}{sup {minus}}, I{sub 3}{sup {minus}}) and {kappa}-(MDT-TTF){sub 2}AuI{sub 2} but a bond-over-bond arrangement in the nonsuperconducting salt {kappa}-(BEDT-TTF){sub 2}Au(CN){sub 2}, so that the intradimer spacing is considerably larger in the nonsuperconducting than in the superconducting {kappa}-phases. The terminal ethylene groups of BEDT-TTF have a staggered arrangement in the high-T{sub c} salts {kappa}-(BEDT-TTF){sub 2}Cu(NCS){sub 2} (T{sub c} = 10.4 K) and {beta}*-(BEDT-TTF){sub 2}I{sub 3} (T{sub c} = {approximately} 8 K) but are eclipsed in the low-T{sub c} salts {kappa}(BEDT-TTF){sub 2}I{sub 3} (T{sub c} = 3.6 K), {beta}-(BEDT-TTF){sub 2}AuI{sub 2} (T{sub c} = 5.0 K), and {beta}-(BEDT-TTF){sub 2}IBr{sub 2} (T{sub c} = 2.8 K). All the Fermi surfaces of the {kappa}-phase can be described in terms of overlapping distorted circles and hence are essentially two-dimensional in nature. However, the Fermi surface of the nonsuperconducting {kappa}-phase, {kappa}-(BMDT-TTF){sub 2}Au(CN){sub 2} exhibits a partial nesting in contrast to the case of the superconducting {kappa}-phases, which is probably responsible for the metal-insulator transition at {approximately} 60 K. 26 refs., 8 figs., 2 tabs.