A computer simulation study of anisotropic molecular models

In this thesis we present a sequence of four computer simulation studies of molecular systems composed of anisotropic molecules. They are linked by a common theme; a study of the behaviour of aggregates of anisotropic particles, with particular attention paid to the possibility of observing a nematic/isotropic phase transition.The eight chapters contained in the thesis naturally divide into three parts. The first four chapters describe the general properties and molecular structure of liquid crystalline mesophases; the statistical mechanical formalism used in their theoretical description; the general techniques of molecular simulation, and the molecular field theory. These chapters provide the descriptive and theoretical framework used in the discussion of the subsequent chapters, which present the results of the simulations.In the second part of the thesis, chapters five and six, we present the simualtion of two different lattice models, using the Monte-Carlo technique. In chapter five we present the simulation of a planar triangular lattice of apolar particles rotating in the plance of the lattice and develop a spin-wave theory to describe the low temperature phase. In the second lattice calculation, a cubic lattice of apolar particles with three dimensional rotational freedom, we study the systematic effects of altering the system size, and use two theoretical methods of inerpreting these effects.In the final section we present two molecular dynamics simulations of non-lattice models. Li chapter seven, we investigate the possibility that the model of a real anisotropic system, carbon disulphide, may form a metastable liquid crystalline phase at low temperatures. Finally, in chapter eight, we present the simulation of a relatively realistic model of a nemato-genic system and discuss its dynamic and static properties. (DX84527)