Elucidation of structural changes and concentration fluctuations in binary mixtures using new thermodynamic relations

The thermodynamics associated with structural changes in binary mixtures has been examined in search of relations which connect Darken stability or the concentration-concentration fluctuations to the thermodynamic response functions. New relations have been derived. These are the counterpart of Ehrenfest relations in an extended form for second order phase transitions in binary mixtures. It has been proved that the structural change inevitably causes instability of a binary mixture with respect to the concentration fluctuations. The new relations make it possible that the instability brought about by structural change can be evaluated in terms of the thermodynamic functions.