MOLECULAR DYNAMICS OF WEAKLY COUPLED ELECTRIC DIPOLES ON A RIGID LATTICE .2. DIELECTRIC RESPONSE FUNCTION

The dielectric response function of a finite two-dimensional system of dipoles is evaluated numerically by the method of molecular dynamics. The dipoles are located on the sites of a rigid square lattice and are only allowed to rotate; the specimen itself is circular and includes 101, 193, or 421 dipoles. Two types of coupling are considered: (a) dipolar interactions and (b) classical exchange interactions favoring either parallel or antiparallel alignment. The corresponding response functions are largely different in each case. For dipolar interactions they differ rather little from the response function corresponding to zero coupling and the influence of the long-range part of the potential seems negligible. On the contrary, exchange interactions lead to response functions which deviate strongly from the zero-coupling limit, even when the coupling is rather weak. The Fourier transforms of these response functions and the corresponding ColeCole diagrams are constructed and discussed as well.