I have been looking into how to interpret and model a complex capacitance as returned in FasterCap via the GetConductance method. The Help dialog says the following:
The array contains the imaginary part of the complex capacitance matrix as calculated by FasterCap (i.e. the conductance divided by 2*pi*f, where pi is pi greek and f is the frequency of interest).
There doesn't seem to be any other reference on how to interpret this data with regards to FasterCap. My assumption, per other resources, is to model this frequency dependent conductance as a resistance (where R=1/G and G=Imaj(Cij)*2*pi*f) in parallel to the extracted capacitance. The results seem reasonable, but I wanted to verify before making any incorrect assumptions. In literature and on the internet, capacitor loss may be modeled as either an ESR or a parallel conductance, or both.