Phase change, second-order, mean-field theory

MEAN-FIELD THEORIES OF THE SECOND-ORDER, PHASE-CHANGE... 

In this section we give the freeon theory of ferromagnetism. As pointed about above ferromagnetism is a second order-phase change which is well-defined by mean-field theory. In Section 6.2 we give the uniform interaction derivation of mean-field theory and in Section 6.3 we compare prediction with observation. 

The question of whether the normally first-order smectic-A to nematic phase transition can be second order in some materials is somewhat controversial. All of the published mean-field theories " of the smectic-A phase do exhibit second-order phase changes for certain values of the potential parameters. In both McMillan s theory and that of Lee et al, the second-order transition is predicted to occur at that end of homologous series having short chain lengths. More specifically, these models predict the second-order changes to occur when the ratio of transition temperatures Tan/Tni (or Tac/Tci) is at or below about 0.88 (see Fig. 5). 

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