摘要:

The TCNQ simple salt derived from the Toluidine Blue cation shows highly unusual magnetic properties. The finely powdered material moves in response to a hand held magnet. However the magnetic susceptibility measured on a Faraday balance is largely temperature independent above the Curie tail and is not abnormally large. Unusually the magnetic susceptibility saturates at around 1T, which is consistent with chains of spins having strong ferromagnetic coupling and a high S value, typically around 100.

ISSN:1058-725X    

DOI:10.1080/10587259208047046

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

摘要:

Model calculations are described for both pure (MX) and mixed-halide (MXxX′1-x) halogen (X)-bridged transition metal (M) linear chain complexes in terms of an extended Peierls-Hubbard, tight-binding Hamiltonian with ¾-filling oftwo-bands. Both inter- and intra-site electron-phonon coupling are included as well as various electron correlations. Calculated properties include electronic (optical absorption), lattice dynamic (IR, Raman) and spin (ESR) signatures for the ground states, localized excited states produced by impurities, doping or photo-excitation-excitons, polarons, bipolarons, solitons; and the edge states (which occur in mixed-halide crystals, e.g. PtClxBr1-x). Adiabatic molecular dynamics is used to explore photodecay channels.

ISSN:1058-725X    

DOI:10.1080/10587259208047047

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

摘要:

Control of the amplitude of CDW has been made by making use of chemical modifications in the halogen-bridged metal complexes. The dynamics of the spin soliton originated from the CT instability is discussed on the basis of the results of the ESR measurements on the complexes locating near the boundary between the mixed-valence state and the mono-valence state.

ISSN:1058-725X    

DOI:10.1080/10587259208047048

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

摘要:

Twenty years ago, if someone had asked for a material with which they could fabricate a yoghurt pot, as quickly as they could with polyethylene, but had the electrical properties as if it were made of aluminium, both chemists and physicists would have laughed them away. Today, we have conductive polymers which can rival copper as a conductor, and materials which can be processed in simple ways, however, the yoghurt pot still seems a little to technical at present! At the forefront of this field, one increasingly finds polyaniline (PANi). The polymer can be processed [l], and is air stable, making it a good candidate for many electrical applications. Along with these most desirable properties, PANi and its family members also have a large number of interesting optical properties, and it is to these that research groups are now turning. In this lecture, I will review some of the salent points about the optical nature of PANi, and hopefully point out some of the potential avenues that they might take us down in the future.

ISSN:1058-725X    

DOI:10.1080/10587259208047049

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

摘要:

A unified view of the metallic state in polyaniline and heavily-doped polacetylene is presented. We first consider a single randomly-protonated strand of the emeraldine form of polyaniline. We show explicitly that the disorder inherent in this system is described by the random-dimer model of Dunlap, Wu and Phillips1. The random dimer model is simply a tight-binding model for a binary alloy in which pairs of lattice sites are assigned one of two values at random. The random dimer model is shown to possess a narrow band of conducting states that can ultimately lead to dramatic increases in the conductivity if the Fermi level is appropriately tuned. It is demonstrated explicitly that the location in the energy band of the conducting states of the random-dimer model for polyaniline coincides with recent calculations of the location of the Fermi level in the protonated form of the polymer2,3. We argue then that the random-dimer model is capable of explaining the insulator-metal transition in polyaniline. In the context of polyacetylene, we propose a ‘dirty metal’ picture for the metallic state which is consistent with both the closing of the band gap and the existence of a band of extended states. Our model is based on the observation that a random distribution of solitons closes the band gap at ∼5-6% doping and is formally equivalent to the random dimer model. The location of the extended states in the disordered soliton lattice is computed. It is shown that because these states lie in the vicinity of the band edge, they are capable of explaining the sudden onset of the experimentally-observed Pauli susceptibility and the subsequent depinning of the solitons in the metallic state. We close by noting that because the random dimer model applies to any lattice in which the defects are extended and possess a plane of symmetry, it quite generally describes any polymeric system in which the stable defects are solitonic or bi-polaronic in nature

ISSN:1058-725X    

DOI:10.1080/10587259208047050

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

摘要:

Two theoretical models for the linear and nonlinear response of quasi-1D organic systems are critically investigated in comparison with experiments. The anomalous dielectric properties and the nonlinear switching phenomenon are discussed from the viewpoint of the soliton motion and the interchain coupling.

ISSN:1058-725X    

DOI:10.1080/10587259208047051

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

摘要:

A new type of single-component organic compounds, BTQBT (Bis[1, 2, 5]-thiadiazolo-p-quinobis (1, 3-dithiole)), has been synthesized. The conductivities of the single crystals ace remarkably high and anisotropic. The observation of the Hall effect is quite unusual in familiar organic semiconductors including the charge transfer complexes.

ISSN:1058-725X    

DOI:10.1080/10587259208047052

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

摘要:

Thin films of conducting radical ion salts (RIS) with predefined anisotropic behaviour have been investigated with respect to their optical and electronic properties. Photoinduced differences in the film growth enable the preparation of conducting structures in these thin films.

ISSN:1058-725X    

DOI:10.1080/10587259208047053

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

摘要:

The diacetylene with stable α-nitronyl nitroxide as side group was synthesízad and polymerized by heating. The magnetic properties of the polymer were measured, and it was assumed that this organic polymer is in the spin glass state.

ISSN:1058-725X    

DOI:10.1080/10587259208047054

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

摘要:

Quantum motions of protons in organic crystalline solids are monitored via the optical transitions of suitable dye molecules coupled to the potential governing the proton motion. Tunneling splittings are determined using line-narrowing techniques and the relaxation dynamics is measured on timescales extending from picoseconds to hours. The relevance of these properties for material uses is discussed.

ISSN:1058-725X    

DOI:10.1080/10587259208047055

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor