title: Tetrahedratic mesophases, chiral order, and helical domains induced by quadrupolar and octupolar interactions.
abstract: We present an exhaustive account of phases and phase transitions that can be stabilized in the recently introduced generalized Lebwohl-Lasher model with quadrupolar and octupolar microscopic interactions [L. Longa, G. Pająk, and T. Wydro, Phys. Rev. E 79, 040701(R) (2009)]. A complete mean-field analysis of the model, along with Monte Carlo simulations allows us to identify four distinct classes of the phase diagrams with a number of multicritical points where, in addition to the standard uniaxial and biaxial nematic phases, the other nematic like phases are stabilized. These involve, among the others, tetrahedratic (T), nematic tetrahedratic (N(T)), and chiral nematic tetrahedratic (N(T)(*)) phases of global T(d), D(2d), and D(2) symmetry, respectively. Molecular order parameters and correlation functions in these phases are determined. We conclude with generalizations of the model that give a simple molecular interpretation of macroscopic regions with opposite optical activity (ambidextrous chirality), observed, e.g., in bent-core systems. An estimate of the helical pitch in the N(T)(*) phase is also given.
authors.affiliation: Marian Smoluchowski Institute of Physics, Department of Statistical Physics and Mark Kac Center for Complex Systems Research, Jagiellonian University, Reymonta 4, Kraków, Poland.
authors.forename: Karol
authors.initials: K
authors.lastname: Trojanowski
authors.forename: Grzegorz
authors.initials: G
authors.lastname: Pająk
authors.forename: Lech
authors.initials: L
authors.lastname: Longa
authors.forename: Thomas
authors.initials: T
authors.lastname: Wydro
mesh_terms: D003198:Computer Simulation; D050866:Liquid Crystals / Q000737:chemistry*; D046911:Macromolecular Substances / Q000737:chemistry; D008956:Models, Chemical; D008958:Models, Molecular; D008968:Molecular Conformation; D044367:Phase Transition; D013499:Surface Properties
chemical_list: D046911:Macromolecular Substances