Showing papers by "Luciano Pietronero published in 1981"

Bond-Length Change as a Tool to Determine Charge Transfer and Electron-Phonon Coupling in Graphite Intercalation Compounds

Abstract: A theory is formulated that explains the observed bond-length change in graphite intercalation compounds in terms of the charge transfer $f$. The values of $f$ obtained via the bond-length changes are in good agreement with those derived with other methods. The present analysis also provides information on the electron-phonon coupling that defines the maximum conductivity.

Configurational excitations and low-temperature specific heat of the Frenkel-Kontorova model

Abstract: We study the specific heat due to configurational changes in a Frenkel-Kontorova model with a finite density of defects. This model provides an example of intermediate disorder related only to the diffusing ions. The results show that it is possible to obtain excitations with very low energy due to quasidegenerate configurations, but it is not possible to obtain a smooth distribution for these energies. The present model applied to the one-dimensional ionic conductor hollandite can very well describe the peak structure recently observed in the low-temperature specific heat.

Mechanisms of electron-phonon scattering and resistivity in graphite intercalation compounds

Abstract: Recently reported data on the resistivity and its temperature dependence of ${\mathrm{C}}_{8}$As${\mathrm{F}}_{5}$ are interpreted in terms of a microscopic theory of the electron-phonon scattering. The theory includes the scattering by the graphite phonons within a tight-binding framework and that by the modes of the charged intercalate for which the anisotropic screening is explicitly considered.

Intercalated graphite: A synthetic metal II. Theory of bond length change and conductivity

Abstract: We present a brief review of the present understanding of the electronic properties of graphite intercalation compounds with special attention on bond length changes and electrical conductivity. After a discussion of the band structure and the Fermi surface we show how to extract the values of the charge transfer and information about the electron phonon coupling from the change of the in plane bond length. These values are then used in the variational solution of the Boltzmann equation to compute the resistivity due to the scattering with the in plane phonons and to estimate the maximum ideal conductivity for these compounds. The comparison with experiments is discussed and the main open problems are outlined.

Effect of Relaxation on some Thermodynamic Properties of Lattice Gas Models with Applications to AgCrS2 and Hollandite

Abstract: Recently, various aspects of interacting particles moving in a periodic substrate potential have been investigated Many papers have considered the commensurate-incommensurate transition within various restricted assumptions (Restriction to T=0 [1–3], continuum approximation [3–5], low temperatures [6–7]) Studies of the order-disorder regime have been restricted mainly to one dimensional models [8–10] Here we want to discuss some aspects of this problem for one and two dimensional models In order to discuss the order-disorder regime, we have chosen to relate the original Hamiltonian to an effective Cluster Hamiltonian Then, standard methods can be applied In the following we show how this can be achieved for two specific examples