Asymptotic description of schematic models for CKN

The fits of 0.4Ca(NO3)20.6 K(NO3) (CKN) by schematic mode-coupling models [V. Krakoviack, C. Alba-Simionesco, J. Chem. Phys. 117 (2002), 2161] are analyzed by asymptotic expansions. The validity of both the power-law and the Cole–Cole-peak solutions for the critical spectrum are investigated. It is found that the critical spectrum derived from the fits is described by both expansions equally well when both expansions are carried out up to next-to-leading order. The expansions up to this order describe the data for 373 K over two orders of magnitude in frequency. In this regime an effective power-law ωa can be identified where the observed exponent a is smaller than its calculated value by about 15%; this finding can be explained by corrections to the leading-order terms in the asymptotic expansions. For higher temperatures, even smaller effective exponents are caused by a crossover to the alpha-peak spectrum.