Crystal structure, band structure and electrical properties of κ-(BEDT-TTF)2SbF6 grown on a Si(001) electrode (original) (raw)
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A new crystal structure for (BEDT-TTF)2SbF6 and some of its physical properties
Bulletin of Materials Science, 2005
A new crystal structure for bis(ethylenedithio)tetrathiafulvalene [(BEDT-TTF) 2 SbF 6 ] was determined by single crystal X-ray diffraction. The crystal structure was refined in the P 1 space group at room temperature. Crystal data for new structure are as follows: triclinic, a = 8⋅ ⋅670 (2) Å, b = 8⋅ ⋅664 (2) Å, c = 16⋅ ⋅842 (5) Å, α α = 89°°⋅ ⋅29 (2), β β = 90°°⋅ ⋅71 (3), γ γ = 92°°⋅ ⋅67 (1), V = 1263⋅ ⋅64 Å 3 , Z = 2, D x = 2⋅ ⋅136 g cm-3 , (Mo-Kα α), λ λ = 0⋅ ⋅7107 Å, R = 0⋅ ⋅057 for a total of 5517 independent reflections. The donors form a trimerized column, and the band structure calculated by the tight-binding approximation shows band insulator properties. The temperature dependent of the d.c. resistivity shows a semiconducting behaviour with room temperature resistivity along the c-axis; ρ ρ 290 K = 5⋅ ⋅6 ohm cm. Keywords. Organic conductors; β β-(ET) 2 PF 6 ; (ET 2)SbF 6 ; electrocrystallization.
Journal of Solid State Chemistry, 2016
Ion mobility, phase transitions, structure, and conductivity in the K 0.7 M 0.3 SbF 4 (M = Rb, NH 4) compounds were studied by NMR spectroscopy, DSC, X-ray, and conductivity measurements. The predominant form in the ion motions resulting from the phase transition of high modification was diffusion of fluoride and ammonium ions above 450 K. The hightemperature phases of K 0.7 M 0.3 SbF 4 (M = Rb, NH 4) are superionic, while their conductivity attains the values of ~ 10-2-10-4 S/cm at 450-500 K. The structures of αand β-modifications of the K 0.7 Rb 0.3 SbF 4 are monoclinic (space group P2 1 /m). The main structural units in them are statistically substituting each other K + and Rb + cations and complex 4 1 SbF anions linked into zigzag-like chains by bridge fluorine atoms. The nearest surrounding of each antimony atom contains five fluorine atoms, so that the antimony coordination polyhedron can be described, taking into account the lone electron pair, as a distorted SbF 5 E octahedron (ψ-octahedron).
Studies of mixed electronic-ionic conductors in BEDT-TTF family compounds
Synthetic Metals, 1993
Some of the salts of BEDT-TTF (or ET) family namely ET2Cu516, ET3CuC14xH20 and ET3AgxI 8 are good mixed electron-group Ib ion conductors. Due to the presence of frozen disorder in anion layer none of the salts is a superconductor, though the first two remain metallic properties down to lowest temperatures. Disorder and non stoichiometry effect on electron transport properties of ET2Cu5I 6 compound have been studied. ESR studies of ET2Ou5I 6 salt show that the line width is strongly increased by the disorder.
Charge transfer in films of (BEDT-TTF)—based molecular conductors as seen by Raman spectroscopy
Journal of Molecular Structure, 2006
The films of (BEDT-TTF) 2 XF 6 (where XZP, Sb) and (BEDT-TTF)[Ni(dmit) 2 ] 2 were electrodeposited on an intrinsic Si(001) electrode. All samples are examined by scanning electron microscopy, X-ray diffraction data and Raman spectra. The results evidence that new (BEDT-TTF) 2 SbF 6 and (BEDT-TTF)[Ni(dmit) 2 ] 2 phases (compared to those obtained on a common Pt wire) are grown on the silicon electrode. q
CrystEngComm, 2011
A modified procedure for the electrocrystallization of organic conductors with paramagnetic anions of the (BEDT-TTF) 4 A I [M III (C 2 O 4 ) 3 ]$G family has been proposed. It is found that single crystals of different phases of the family can be prepared if the electrocrystallization medium is represented by the mixture of 1,2,4-trichlorobenzene (or 1,3-dibromobenzene), 96% ethanol and different solvents (G), only the latter being included into the composition of the resulting salts as neutral guest molecules (G ¼ benzonitrile, fluorobenzene, chlorobenzene, 1,2-dichlorobenzene, bromobenzene, nitrobenzene). Using this approach, a number of known and new BEDT-TTF salts with the tris(oxalato)ferrate anion have been synthesized. Among them, there are superconducting crystals of monoclinic b 00 -series with different guest solvents (G) and their mixtures. For the first time, crystals of a triclinic phase (G ¼ 1,2-dibromobenzene), with alternating aand 'pseudo-k' BEDT-TTF layers and metallic behaviour down to 1.5 K, were obtained. Additionally, monoclinic crystals having another stoichiometry and a-type donor packing were prepared.
Electronic and Phonon Properties of BaF[sub 2] Studied By Density Functional Methods
2011
Ground state properties of face centered cubic fluorite BaF 2 is investigated using first principle method. The calculated lattice constants, bulk modulus are reported and compared with available experimental and theoretical data. The band structure and electronic density of states conforms that the BaF 2 is ionic. The phonon dispersion and phonon density of states are also presented and analyzed.
Chemistry of Materials, 2008
Electrochemical oxidation of 4,5-ethylenedioxy-4′-methyl-tetrathiafulvalene (MeEDO-TTF) afforded three types of (MeEDO-TTF) 2 PF 6 radical cation salts under different conditions: black powder, dark green plates, and black plates. The optical absorption spectra of these modifications were very similar to each other. The black powder and dark-green plate modifications were semiconducting and metallic, respectively, and the latter showed a semiconducting behavior below 200 K. The black plate modification exhibited a semiconductor-to-semiconductor first-order phase transition at around room temperature (303 K). The donor molecules in both the high-and low-temperature phases of this modification showed similar packing patterns, based on which the tight-binding approximation afforded similar two-dimensional Fermi surfaces. The phase transition of this modification is accompanied by a subtle change in the relative orientation of the neighboring donor molecules. The vibrational spectra proved that a nearly localized charge disproportionation takes place in the high-temperature phase and the distinct charge disproportionation is developed in the low-temperature phase. These results indicate that the slight lattice distortion assists the stabilization of charge disproportionation. The comparison of the isostructural salts of metallic (MeEDO-TTF) 2 X (X ) BF 4 , ClO 4 ) and the semiconducting high-temperature phase of the (MeEDO-TTF) 2 PF 6 demonstrated that the side-by-side intermolecular interaction is most effectively modulated according to the anion size. The unit cell parameter corresponding to this intermolecular interaction was varied only ca. 2% among these isostructural salts. This observation demonstrates the very sensitive nature of the transport property to the lattice modulation. (a) Williams, J. M.; Ferraro, J.; Thorn, R. J.; Carlson, K. D.; Geiser, U.; Wang, H.-H.; Kini, A. M.; Wangbo, M. H. Organic Superconductors (including Fullerenes); Prentice Hall: Englewood Cliffs, NJ, 1992. (b) Ishiguro, T.; Yamaji, K.; Saito, G. Organic Superconductors, 2nd ed.; Springer-Verlag: Berlin, 1998.
Multistability in a BEDT-TTF Based Molecular Conductor
Journal of the American Chemical Society, 2003
The low dimensional organic conductor (BEDT-TTF)(2)Br(1.3)I(1.1)Cl(0.6) [BEDT-TTF = bis(ethylenedithio)tertathiafulvalene] is shown to be a unique molecular solid that exists in three crystalline polymorphic forms (alpha'-, alpha' "-, beta' '-phase) and, surprisingly, is able to adopt the same metal-like beta' '-phase at both low (T < 185 K) and high (T > 395 K) temperatures. Several crystals of the alpha'- and alpha' "-phases have been studied using three different techniques: dc-conductivity measurements, ESR spectroscopy, and X-ray diffraction analysis. All these techniques show the existence of the reversible semiconductor <--> metal (alpha' " <--> beta' ') phase transition at both high and low temperatures as well as the alpha' <--> alpha' " phase transition at high temperatures. The phase transitions of these polymorphs are characterized by huge hysteresis and dramatic changes in the transport and magnetic properties. Based on ab initio calculations, it is suggested that dipole-dipole interactions can play a key role in the rich polymorphism of this molecular solid.
Transport properties and phase transition of organic crystal βd′ -(BEDT-TTF)2I3
Synthetic Metals, 1989
A peculiar resistivity anomaly has been observed in a new phase of (BEDT-TTF)2I 3 first synthesized recently by Zhu et al. using a diffusion method. The structure of the new phase is similar to that of its isomer ~-(BEDT-TTF)213, with a slightly different arrangement of iodine atoms and lattice constants. But, in contrast to the H-phase, which remains metallic when the temperature decreases and finally becomes a superconductor, the new phase undergoes a metal-semiconductor transition at about 140 K. Then, after a rapid rise, the resistivity peaks at ~60 K. However, the thermopower measurement shows only a small anomaly at the phase transition. A model with two energy bands is assumed to explain these phenomena. The quite different behaviour of the new phase seems to imply that the iodine anion plays a subtle role in the determination of the properties of the material.