FORCES IN AN INHOMOGENEOUSLY ORDERED NEMATIC LIQUID-CRYSTAL - STABLE AND METASTABLE STATES

Forces on plates separated a few nanometers and immersed in an isotrop ic liquid crystal are examined within a continuum approximation. The s urface induced partial ordering of a liquid crystal is described using Landau-de Gennes phenomenological theory. Phase diagrams are presente d to show the effect of surface coupling parameters, distance between the plates, and temperature on the stability and metastability of nema tic and isotropic phases. Special attention is paid to the appearance of metastable phases. For selected examples we study distance and temp erature dependences of the force. Values of surface coupling parameter s are chosen in agreement with the results of recent experiments. For large distances between the plates the force scales with the second po wer of the surface coupling parameters and becomes an exponentially de creasing function of distance characterized with the nematic correlati on length.