Simple Landau model of the R(IV)-R(III)-R(V) rotator phases of alkanes.

Simple Landau-type free energy function is presented to describe the R(IV)-R(III)-R(V) rotator phase sequence and the transitions between them. The order parameters necessary to describe the above rotator phase transitions are identified. Varying the coupling between the order parameters, the R(IV)-R(III) and R(III)-R(V) transitions occur. Available experimental results are consistent with our model.