In this paper, molecular dynamics simulations are employed to study the liquid-crystal phases of 2-(4-butyloxyphenyl)-5-octyloxypyrimidine and 5-(4-butyloxyphenyl)-2-octyloxypyrimidine. Both mesogens consist of aromatic phenyl-pyrimidine cores in between two identical alkoxy tails, but they differ in the preferred core conformation. The ab initio–based derivation of suitable molecular models is discussed in detail, with particular emphasis on capturing proper ring-ring interactions. The presence of ring quadrupoles in the molecular model is shown to be essential to the correct reproduction of the experimentally observed phases. Simulations of these fluids at various temperatures are performed and order, for the aromatic core and the flexible tails, is analyzed. To differentiate smectic-$A$ from smectic-$C$ phases, intermolecular structure is divided into contributions parallel and perpendicular to the director and layer normal.

• Received 24 November 2009

DOI:https://doi.org/10.1103/PhysRevE.81.041704