MOLECULAR-DYNAMICS SIMULATIONS OF LIQUID-CRYSTAL PHASES USING ATOMISTIC POTENTIALS

Molecular dynamics simulations have been carried out for the liquid cr ystal molecule 4,4'-di-n-pentyl-bibicyclo[2.2.2]octane (5,5-BBCO). A u nited-atom model was employed with the central bicyclooctane groups in the core of 5,5-BBCO modelled as rigid units using a quaternion leapf rog algorithm in combination with bond length constraints, making use of the QSHAKE (er;tension to SHAKE) algorithm. Results are presented f or the structure and :dynamics of (5,5-BBCO) at a series of state poin ts in the range 200-500 K for sample sizes of 64 and 125 molecules, an d run lengths of up to 12 ns. The growth of orientational order direct ly from the isotropic phase is found to be extremely slow, taking plac e over a period of 6-10 ns. This phase change is accompanied by major conformational changes in the molecules themselves.