Landau model of the R_(II)-R_IR_V rotator phases in mixtures of alkanes

摘要

A phenomenological approach to the description of the rotator phases and transitions among them in mixtures of normal alkanes is proposed.The mixture exhibits crystal and three different rotator phases R_(II),R_I,and R_V.The two phase regions are formed where the crystal+rotator and rotator+rotator phases coexist.The reason of these two phase regions is discussed by means of the Landau formalism.The influence of the concentration on these transitions and the transition temperatures are discussed by varying the coupling between the concentration variable and the order parameters.The theoretical predictions are found to be in good qualitative agreement with the experimental results.