Crystallization phase transitions and phase diagram of Langmuir monolayers

Abstract

Seven structurally distinct condensed phases in the phase diagram of water-supported Langmuir monolayers are explained in the framework of the Landau theory of phase transitions. The present treatment, which covers two-dimensional hexatic and solid phases and describes the transitions between them, involves the coupling of three order parameters. One of the parameters governs the collective tilt of the molecules, while the other two describe one-dimensional ``weak crystallization'' along the bond direction and normal to it with the herringbone ordering of the molecular backbone planes.