The following CHARMM script and Fortran program are used together to compute the dielectric constant of cubic systems; I've been using them to evaluate developmental parameters on simulations of neat fluids. The script is used to create a vector time series of the system dipole using COOR DIPOLE (corman.doc) in a loop over frames. The Fortran program computes eps from that time series, and outputs the cumulative value of eps vs. time as a text data file suitable for plotting. There's some unit conversion going on the program, from AKMA into SI units.

Rick Venable
computational chemist