Miscibility gaps, ordered liquids and liquid semiconductors

Liquid miscibility gaps in binary systems which also contain compounds are considered. It is assumed that the miscibility gap is caused by ordering of the liquid in certain composition ranges. Three models are postulated; overall order, formation of uniformly shaped clusters and formation of elongated clusters. General conditions for the cluster models to lead to miscibility gaps are investigated. One condition is that the concentration of clusters is high over a fairly large composition range, and this may be important for some liquid semiconductors.