Potential barrier and conductivity

The direct conductivity, o, is given by the response of the system to a longitudinal electric field parallel to the direction of diffusion of the 

Conductivity can be deduced from vibrational spectra in IR spectroscopy, the absorption coefficient a(co) is related to tr(co) a(o)) = 4no(o))/nc, n being the refractive index and c the velocity of light. In Raman spectroscopy, the scattered intensity /(m) is related to conductivity by a(o ) oc o)I (o)/n(a)) + 1, n(co) being the Bose-Einstein population factor . Finally, the inelastic incoherent neutron scattering function P(o)) is proportional to the Fourier transform of the current correlation function of the mobile ions. P co) is homogeneous with a) /(cu) formalism. However, since P(co) reflects mainly single particle motions, its comparison with ff(co) could provide a method for the evaluation of correlation effects. (For further discussion, see also Chapter 9 and p. 333.) 

There is an extensive literature on the application of vibrational spectroscopy to phase transition investigations. The phase transitions in proton conductors can be studied in much the same way as in other crystals as far as the order, nature and mechanism are concerned. Particularly interesting examples are those of HUP, CSHSO4, (NH4)3H(S04)2 and NH4HSe04 described in Chapters 11 and 17. 

Hamilton and J. A. Ibers, Hydrogen Bonding in Solids (New York, 

Hadzi and S. Bratos, in The Hydrogen Bond II, P. Schuster, G. Zundel and C. Sandorfy (eds.) (North-Holland Publishing (1979)) 565. 

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