A computer simulation study of tilted smectic mesophases

We present comprehensive results from constant NVT and constant NPT Monte C arlo simulations of particles interacting via a biaxial variant of the Gay- Berne potential which we term the Internally Rotated Gay-Berne (IRGB) poten tial. The IRGB potential may be considered to be a single-site approximatio n to the interaction between two zig-zag shaped molecules, the extent of th is molecular biaxiality being characterized by an internal rotation angle d elta. We find that increasing the value of delta frustrates the formation o f orientationally ordered phases, all phase transitions being shifted to lo wer temperatures and higher densities. Additionally, for delta greater than or equal to 30 degrees, the smectic B phase is replaced by the tilted smec tic J phase. The smectic A phase, in contrast, is destabilized completely f or sufficiently large delta, with neither smectic A nor its tilted equivale nt, smectic C, being observed. This suggests that models for smectic C-form ation which are based on biaxial intermolecular attractions may not offer t he best route to obtaining this phase. (C) 2000 American Institute of Physi cs. [S0021-9606(00)50636-9].