Abstract
In the glass-forming ionic melt 2 Ca(NO 3 ) 2 .3 KNO 3 , often abbreviated as CKN, the dc conductivity, σ d c (T), is markedly non-Arrhenius at temperatures above 375 K, making this system one of the classical examples of 'fragile' molten salts. The following observations on CKN are no less remarkable. (i) In contrast to σ d σ (T), the non-vibrational high-frequency limiting conductivity, σ h (T), is exactly Arrhenius. (ii) The functions E a (T) = k B T 2 . (∂In(σ d c T)/∂T) p and V a (T) = -k B T.(∂ In(σ d c T)/∂p) T which in a formal sense may be regarded as 'activation energy' and 'activation volume', display identical temperature dependences, their ratio being temperature independent. All these features, as well as the frequency dependence of the conductivity, are consistently explained in a simple model describing the ion dynamics in fragile molten salts. The model treatment is based on the MIGRATION concept. The meaning of the acronym is MIsmatch Generated Relaxation for the Accommodation and Transport of IONs.
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