Groupe de Physique Statistique/ Arbeitsgruppe Statistische Physik

Relationship between molecular interactions and relative stability of the corresponding liquid crystalline phases is still not fully understood. A direct and reliable way to account for structures that could be induced by specific intermolecular interactions is offered by computer simulations. A purpose of this lecture is to discuss this issue, in particular the effect of dispersion and dipolar forces on mesophase formation and stability as derived from computer simulations. We are going to concentrate on effects that result from such forces by studying Gay-Berne molecules with embedded dipole moments. In particular, the stability of smectic A phase as function of position and strength of the dipole moment will be discussed. Emphasis is put on the role played by correlation functions in a proper understanding of the structures. One of the interesting observations is the presence of stable smectic Ad-phase and connection between its layer spacing and dipolar strength. Effects of competition between hexagonal ordering preferred by GB part and tetragonal one connected with the dipoles leads to frustration of the dipoles within smectic layers.