Tricritical behavior of the R(I)-R(V) rotator phase transition in a mixture of alkanes with nanoparticles

A phenomenological theory is presented, which describes the tricritical behavior of the R(I)-R(V) rotator phase transition in the mixture of alkanes with nanoparticles. The influence of the nanoparticles on the R(I)-R(V) transition in alkanes is discussed by varying the coupling between the order parameters of the rotator phases and nanoparticle. When nanoparticle solutes are added to pure alkanes, the R(I)-R(V) transition temperature is increased. It was observed from the theoretical calculations that for a particular value of the concentration of the nanoparticles, the first order R(I)-R(V) transition becomes second order at a tricritical point. Calculations based on this model agree qualitatively with experiment.