LONG-RANGE FORCES AND AGGREGATION OF COLLOID PARTICLES IN A NEMATIC LIQUID-CRYSTAL

We calculate the long-range pair potential between spherical colloid p articles suspended in a uniform liquid crystal. At weak director ancho ring on the particle surface the director distortions decay as delta n similar to r(-3)sin2 theta away from its center. This leads to an ani sotropic interaction potential of the form U similar to d(-5) with d t he distance between two colloid particles. This interaction also depen ds on the particle position with respect to the nematic director, givi ng strong repulsion for particles along the director axis and for part icles located in the perpendicular plane, and attraction at oblique an gles. We also analyze the system behavior in an external field, when t he director decays exponentially away from the particle and, hence, in teraction forces are short range.