In GROMACS, gmx dielectric command can calculate frequency dependent dielectric constants from the autocorrelation function of the total dipole moment in your simulation. Maybe it is useful to you.

For low frequencies, up to some MHz, this can be measured using the capacitance method. However, if the amount of liquid metal is too large the loss factor (ohmic component) becomes unwieldy large and other techniques have to be sought. However, the material is then more a conductor than a dielectic.

Thanks