Hi, I'm trying to model the frequency response of a thin PZT disc using COMSOL, but I am not sure how to calculate the impedance Z vs frequency. I defined the current density at the top electrode as I=-imag(nJ_smpz3d) and then plotted V/I using the domain plot parameters in the postproc menu. This gives me a V/I vs freq plot, but V/I is not equal to Z! Does anybody know how to calculate Z? And the Phase? Thanks!