Simple Landau free energy function is presented to describe the Liquid-RII-RI phase sequence of alkanes and transitions between them. The order parameters necessary to describe these rotator phase transitions are identified. We present a mean-field description of the Liquid-RII and Liquid-RI transitions. General arguments are presented for the topology of the phase diagram in the vicinity of the Liquid-RII-RI triple point. Within this model the Liquid-RII and Liquid-RI transitions are found to be always strongly first order. Calculations based on this model agree qualitatively with experiments.
KeywordsRotator PhasesPhase TransitionsLandau Theory
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