Discussion Forum

Hi all,

I'm doing some impedance spectroscopy with the AC/DC module, ec, in 5.1 on water. Now there are a number of papers that I have referenced which have all used 3.5a to get some polarization and dispersion effects at low frequencies: 1E2 - 1E5.

Namely:
www.sciencedirect.com/science/article/pii/S0956566311005069

Whereby the model is setup as:
Comsol boundary conds.png attached

Generating an E-field and potential distribution as:
1-s2.0-S0956566311005069-mmc1.jpg attached

Resulting in the following dispersion mechanism being observed:
Dispersion at low frequencies.jpg attached.

Now, I get the same E-field and potential distributions, but I do not get the same dispersion, my impedance is just a flat line. This is because Comsol isn't taking into account the fact that the permittivity is frequency dependent.

So, I change the permittivity so that it adheres to the Debye formula for water:
epsilon_r = (4+(81-4)/(1+(freq/20e9[Hz])^2))-(i*((freq/20e9[Hz])*(81-4))/(1+(freq/20e9[Hz])^2))
but of course, this only accounts for one dispersion mechanism, centered around 20e9 Hz, I want to investigate the dispersion mechanism in the range: 1E2 - 1E5..

I know that the RF module has Debye dispersions built in, but I don't want to use emw... I want to use AC/DC and ec like everybody else has. Is this a nuance between v 3.5a ->?

I should also mention that that paper uses a constitutive relation which isn't the relative permittivity, but polarization:
D = (epsilon_0)*E + P
and the default is:
D = (epsilon_0)*(epsilon_r)*E