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Librons in Organic Conductors

1982; Volume: 85; Issue: 1 Linguagem: Inglês

10.1080/00268948208073629

0026-8941

H. Morawitz,

Solid-state spectroscopy and crystallography

Abstract We will review a variety of effects in organic conductors, which arise from the existence of low-lying rotational lattice modes in these materials. A distinction will be made between unambiguous and ambiguous consequences of librational modes. An example of the former is the specific heat, whose value necessarily implies the excitation of low-lying Einstein modes far in excess of the number of existing translational modes. For the latter category of effect, we mention the much debated origin of the temperature dependence of the conductivity. We will also present recent progress in the lattice-dynamical calculation of the entire lattice mode spectrum of segregated stack systems such as TTF-TCNQ and single stack systems such as (TMTSF)2PF6 with emphasis on the mixing of rotational and translational components in the first Brillouin zone by the dynamical matrix. We will also discuss the implications of the phonon-libron hybridization and the specific phase relations between these components for the analysis of the structure factor observed in diffuse x-ray and neutron scattering.