Neldel

Emin D (2008) Generalized adiabatic polaron hopping Meyer-Neldel compensation and Poole-Frenkel behavior. Phys Rev Lett 100 166602... 

Support for the applicability of this model to an explanation of the Meyer-Neldel rule comes from measurements of space-charge limited currents in anthracene where a correlation (see Fig. 20) has been found between the total density of traps H and the distribution parameter Tc (Owen et al, 1974). It has been shown that this effect is not fortuitous as suggested by some workers... 

Fig. 7.3. Measured values of the conductivity prefactor a, versus the conductivity activation energy, showing the Meyer-Neldel relation. Data from sever different laboratories are shown (Tanielian 1982).

The Meyer-Neldel relation is a statement that the temperature dependence data for different samples all intersect at the same value of conductivity, Og, at the temperature 7 x 600 K. There is still no completely satisfactory explanation of why this occurs. 

Therefore, within the linear approximation, the conductivity activation energy Eg measures the value of ( tr— )g and the prefactor contains the additional factor exp(y/k). The temperature dependence of the energies accounts for the Meyer-Neldel relation provided that... 

A more detailed analysis of the conductivity data is needed to explain the prefactor and to understand the Meyer-Neldel relation. The magnitudes of Yp and Yg depend on the location of the Fermi energy, the density of states distribution and the thermal state of the material. There are three situations which can be analyzed easily. 

Yeh T-C, Zhang W, lldstad ST, Ho C (1993) Intracellular labeling of T-cells with superparamagnetic contrast agents. MRM (Magnetic Resonance in Medicine) 30 617-625 Yelon A, Movaghar B (1990) Microscopic explanation of the compensation (Meyer-Neldel) mle. Phys Rev Lett 65 618-620... 

Many organic materials have been reported to follow the Meyer-Neldel Rule (MNR) which is a phenomenological model to describe the observed temperature dependence of the mobility. 

Organic field effect transistors were fabricated based on C60 layers. The temperature dependence of juFE was investigated for different VG. pfe is found to be thermally activated with activation energies strongly dependent on the applied VG. Upon extrapolation of the data in the Arrhenius plot to infinite temperature in the Meyer-Neldel formalism, 7 r = 480 K and pm-i = 2.45 cm2V s 1 can be extracted. The observed temperature dependence of uEE can be explained by empirical MNR, which is based on the assumption of an exponential density of states distribution. 

Equation (5) describes the relationship between the log of the preexponential factor and the activation energy - og(7o(E t), which should be linear and is known as the Mayer-Neldel rule [21, 22], This relationship was first observed for semiconductors and recently for ionic conductors [21, 23], as well as for organic thin film transistors [24], The conductivity plots determined for a family of similar specimens obeying this rule converge to a point at temperature To, which is constant within a class of related materials. The value of To should be related to the material melting point where the hopping energy at T = To approaches zero (Eq.5). 

The phenomenon of compensation is not unique to heterogeneous catalysis it is also seen in homogeneous catalysts, in organic reactions where the solvent is varied and in numerous physical processes such as solid-state diffusion, semiconduction (where it is known as the Meyer-Neldel Rule), and thermionic emission (governed by Richardson s equation ). Indeed it appears that kinetic parameters of any activated process, physical or chemical, are quite liable to exhibit compensation it even applies to the mortality rates of bacteria, as these also obey the Arrhenius equation. It connects with parallel effects in thermodynamics, where entropy and enthalpy terms describing the temperature dependence of equilibrium constants also show compensation. This brings us the area of linear free-energy relationships (LFER), discussion of which is fully covered in the literature, but which need not detain us now. 

There is some correlation between the parameters Dq and Q. The Meyer-Neldel rule says that nDo = abQ, with a and b positive numbers. Dq compensates somewhat for the influence of Q. The higher the activation energy Q, the higher the preexponential factor Dq. 

What is the atomistic reason for the Meyer-Neldel rule Design two ion conductors (for Li" and 0 ) that have a low value for L and simultaneously a high Dq. 

In 2000, Balberg (2000) classified the electrical transport in PS by reanalyzing experimental data collected from various published papers about the temperature dependence of DC dark conductivity, according to Meyer-Neldel rule (MNR)... 

Lubianiker Y, Balberg I (1997) Two Meyer-Neldel rules in porous silicon. Phys Rev Lett 78 2433 Lubianiker Y, Balberg I, Partee J, Shinar J (1996) Porous silicon as a near-ideal disordered semiconductor. J Non-Cryst Solids 198-200 949... 

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