Tight-binding parameters for charge transfer along DNA

We systematically examine all the tight-binding parameters pertinent to charge transfer along DNA. The $\pi$ molecular structure of the four DNA bases (adenine, thymine, cytosine, and guanine) is investigated by using the linear combination of atomic orbitals method with a recently introduced parametrization. The HOMO and LUMO wavefunctions and energies of DNA bases are discussed and then used for calculating the corresponding wavefunctions of the two B-DNA base-pairs (adenine-thymine and guanine-cytosine). The obtained HOMO and LUMO energies of the bases are in good agreement with available experimental values. Our results are then used for estimating the complete set of charge transfer parameters between neighboring bases and also between successive base-pairs, considering all possible combinations between them, for both electrons and holes. The calculated microscopic quantities can be used in mesoscopic theoretical models of electron or hole transfer along the DNA double helix, as they provide the necessary parameters for a tight-binding phenomenological description based on the $\pi$ molecular overlap. We find that usually the hopping parameters for holes are higher in magnitude compared to the ones for electrons, which probably indicates that hole transport along DNA is more favorable than electron transport. Our findings are also compared with existing calculations from first principles.Comment: 15 pages, 3 figures, 7 table

Percolation-theoretic considerations for the thermoelectric power and the conductivity due to small polaron motion in disordered systems

Percolation-theoretic considerations have been used by various workers to evaluate the dc hopping conductivity and the thermoelectric power in disordered systems. We apply percolation theory to the small polaron hopping regime. Expressions for the thermoelectric power at low and high temperatures are obtained for a situation in which we have a symmetrical band of localized states with the Fermi level in the middle, and for an asymmetrical case in which we have a band of localized states above the Fermi level, and the conductivity for the low temperature case is evaluated. The correlation between bonds due to the energy of the common site is included in the present treatment. © 1985

The effect of energy-dependent densities of states and the importance of correlations on the conductivity of the small-polaron hopping regime in disordered systems

We investigate, using percolation arguments, the effect of energy-dependent model densities of states on the d.c. conductivity behaviour in the small-polaron hopping regime, taking into account the fact that the lower-energy states are less ‘dense’. General expressions for T0 and ν, which determine the conductivity (In σ ~ -(T0/T)v), are obtained for the high- and low-temperature regimes, ignoring or taking into account correlations between bonds due to the energy of the common site. For a constant density of states the importance of correlations is revealed by analysing experimental data previously reported for V2O5-P2O5 glasses using In σ against T-2/5 and T-1/4 plots as suggested by the Triberis-Friedman and the Triberis models. The agreement of the experimental data with the theory is very satisfactory. © 1992 Taylor & Francis Ltd

The field dependence of the conductivity for the low-temperature small-polaron hopping regime in disordered systems

The author investigates the effect of an electric field on the conductivity of the low temperature few-phonon-assisted small-polaron hopping regime. The deformation of the surroundings induced by the carrier is taken into account. Comparison is made with other theories. © 1988 IOP Publishing Ltd

The Effect of Temperature and Coupling Strength on the Thermoelectric Power in the Small‐Polaron Hopping Regime

The effect of temperature and coupling strength on the thermoelectric power of the small‐polaron hopping disordered regime is investigated. The thermoelectric power is evaluated for the high‐and low‐temperature case assuming the electron‐lattice interaction to be weak. Results are also given for the low‐temperature and strong‐coupling case. The “macroscopic” thermoelectric power of the material is evaluated for the low‐temperature regime. Copyright © 1986 WILEY‐VCH Verlag GmbH & Co. KGa

A conductivity study on V2O5 layers deposited from gels

Triberis and Friedman applied percolation theory to the small polaron hopping regime and they evaluated the DC conductivity in disordered systems. Correlation due to the energy of the common site in a percolation cluster were included. We analyse the behavior of the DC conductivity of V2O5 thin layers deposited from gels using ln σ versus T- 1 4 plots, as suggested by their model, using experimental data for σ obtained by other workers. The agreement of the experimental data with this model is very satisfactory giving a meaningful interpretation of the transport properties of these materials. The density of states of these V2O5 layers deposited from gels of various V4+ content C is evaluated. © 1988

Thermoelectric Power Due to Small Polaron Hopping Motion in Disordered Systems

A theory is developed of the thermoelectric power associated with electronic phonon‐assisted hopping motion between energetically inequivalent sites with different electron–lattice interaction parameters. The general results are applied to the high‐temperature small polaron hopping case. Comparison is made with other theories. Copyright © 1985 WILEY‐VCH Verlag GmbH & Co. KGa

Thermoelectric Power Due to Small Polaron Hopping Motion in Disordered Systems

A theory is developed of the thermoelectric power associated with electronic phonon‐assisted hopping motion between energetically inequivalent sites with different electron–lattice interaction parameters. The general results are applied to the high‐temperature small polaron hopping case. Comparison is made with other theories. Copyright © 1985 WILEY‐VCH Verlag GmbH & Co. KGa

Phonon-drag thermopower of composite fermions at filling factor 3/2

We present, for the first time, a quantitative interpretation of the measured diagonal thermopower, Sxx, for a 2DEG at filling factor ν = 3/2. The Sxx data span the temperature range 0.2 ≤ T ≤ 1.2 K and show that the phonon-drag thermopower, Sxxg, is the dominant contribution at all T. Sxxg is calculated by using the standard Cantrell-Butcher formalism within the composite fermion picture. The theoretical results for Sxxg agree very well with the experimental data when the value 0.87me for the composite fermion mass at ν = 3/2 is used. We also calculate the ratio Sxxg(ν = 3/2)/Sxxg(ν = 1/2) and we find that it is unity for T ≤ 0.5 K which is in very good agreement with the experiment. © 2002 Elsevier Science B.V. All rights reserved