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Peierls phonons in organic molecular crystals and in charge transfer salts

100%

Girlando A. , Masino M. , Brillante A. , Della Valle R. G. , Venuti E.

tom Vol. 22, No. 4

307--316

We review the Quasi-Harmonic Lattice Dynamic (QHLD) method, which we have recently implemented and adopted to carefully reproduce the crystal structure and lattice phonon dynamics of molecular crystals as a function of temperature and pressure. Association with mean field electronic structure calculations allows us to characterize the Peierls coupling, namely the coupling between electrons and lattice phonons. We apply this method to organic superconductors based on bis-ethylene-dithio-tetrathiafulvalene (BEDT-TTF), showing that many experimental findings related to superconducting properties are rationalized in terms of the Peierls coupling. Electron-intramolecular phonon coupling and electron -electron interactions, however, have to be taken into account for a full characterization. We also present results concerning another class of molecular crystals, the acenes. In this case, the focus is on the understanding of the temperature dependences of mobilities. First and foremost, however, we emphasize the possibility of accurately predicting both the crystal structure and lattice phonon spectral signatures. We analyse pentacene and tetracene, showing that both systems can crystallize into two different polymorphs. The two polymorphs have comparable stabilities, and can coexist in the same crystallite. Raman spectroscopy in the lattice phonon region is used as a convenient tool to identify the two phases. The Peierls coupling strength of pentacene is evaluated.

The Microcrystals of BEDT-TTF and BEDO-TTF Polyiodides Forming the Conducting Networks within Polymer Film surface and Their Transformations

75%

Tracz A.

Polish Journal of Chemistry

2002

tom Vol. 76 / nr 2-3

457-470

New results on morphology and structure of microcrystals of bis-(ethylenedithio)tetrathiafulvalene (BEDT-TTF or ET) and bis(ethylenedioxy)tetrathiafulvalene (BEDO-TTF or BO) polyiodide salts formed within surface layers of polymer films by a two step reticulate doping technique and their transformations are discussed. The architecture of the microcrystalline conducting network was studied by STM and AFM. X-ray diffraction studies of microcrystals of ET salts in polymer matrix and structure-properties relationships are discussed. The thermal transformation of microcrystals of _-ET2I3 in polymer matrix to _-ET2I3 was followed in situ by X-ray diffraction and a new example of the transformation of microcrystals of BO salt in polymer matrix by annealing is shown.

20 Years of Reticulate Doping-Beyond Conductive Properties

63%

Jeszka J.

Polish Journal of Chemistry

2002

tom Vol. 76 / nr 2-3

201-218

The most interesting results obtained during 20 years of studies on reticulate doped polymers preparation and properties are reviewed. All developed methods of preparation are described and the influence of different parameters on the properties of obtained materials is briefly discussed. The stress is put not so much on the electrical properties but on the aspects of preparation and on the properties, which are interesting but deserved less attention till now like structure, morphology and composition of the microcrystals and their transformations, optical, magnetic and other properties.