Query Regarding thermoelectric coefficient calculation

[harkishan_dua]

I want to calculate thermoelectric properties of a 2D material by calculating its electron transmission without considering the phononic part. Because for phonon transmission calculation, we have to first design a device configuration and for that very high computational resources are required.  Now after calculating the electron transmission calculatuions and viewing the results in the virtual nano lab we are getting various thermoelectric coefficients except ZT  which is showing to be Nil. However in the plot, I am obtaining the variation of ZT with respect to energy. So I have doubrt regarding this ZT plot as to where these values are arising from when the value of ZT shown in the nano lab is nil.

[Petr Khomyakov]

Which version of QuantumATK are you using? It would also be helpful to see your python script, log and hdf5 files.

[harkishan_dua]

I am using the QuantumATK Q-2019.12-SP1 version. As per your suggestion, I am attaching the required files in a single .zip file along with this reply.

[Troels-Markussen]

Hi,

Currently the ZT is only shown in the table if both the phonon transmission and electron transmission spectra are available. However, the ZT which is shown in the plot is calculated from the usual formula ZT=G*S^2*T/k_tot,
where k_tot = k_el + k_ph. In the case where the phonon transmission spectrum is not calculated, the phonon thermal conductance, k_ph, is just set to zero.

Notice that often k_ph > k_el, which means that the ZT calculated without the phonon contribution is way too large. However, the values in the plot of ZT are fine, given that you are aware of the overestimation of ZT. In scientific papers, this quantity if sometimes denoted ZT_el, highlighting that it is calculated only from the electronic transmission. The "real" ZT is the ZT  = ZT_el * k_el / (k_el + k_ph).

Regards,
Troels