Instabilities, thermal fluctuations, defects and dislocations in the crystal–RI–RII rotator phase transitions of n-alkanes
Abstract
The theoretical study of instabilities, thermal fluctuations, and topological defects in the crystal–rotator-I–rotator-II (X–RI–RII) phase transitions of n-alkanes has been conducted. First, we examine the nature of the RI–RII phase transition in nanoconfined alkanes. We propose that under confined conditions, the presence of quenched random orientational disorder makes the RI phase unstable. This disorder-mediated transition falls within the Imry-Ma universality class. Next, we discuss the role of thermal fluctuations in certain rotator phases, as well as the influence of dislocations on the X–RI phase transition. Our findings indicate that the herringbone order in the X-phase and the hexatic order in the RII-phase exhibit quasi-long-range characteristics. Furthermore, we find that in two dimensions, the unbinding of dislocations does not result in a disordered liquid state.