problems on thermoelectric calculations

[wot19920302]

  Dear staffs, I meet some problems when studying thermoelectric materials using ATK:
      1.what does T mean in ZT(figure of merit)? environment temperature or difference between hot and cold?
      2.when I use DFT to calculate dynamic matrix to get phonon transmission spetrum so that I can get thermal conductance, I find one term in calculatior setting is to define electrode temperature(top picture,the default is 300K). And when I open the Thermolelctric Coefficients  plugin, I find I can get various thermal conductance by changing temperature T(buttom picture). If I want to get the  thermal conductance in 500K, for example, I can use DFT with 300K, and then set 500K in Thermolelctric Coefficients  plugin; or  I can use DFT with 500K and get thermal conductance directly. which one correct?
   Best regards.
     

[Jess Wellendorff]

1) Please have a look through the literature on thermoelectrics to understand the meaning of the ZT "figure of merit", or simply browse through the wikipedia entry on the subject: https://en.wikipedia.org/wiki/Thermoelectric_materials#Materials_selection_criteria. The ZT is a dimensionless number that indicates the ability of a given material to efficiently produce thermoelectric power. ZT should therefore be as high as possible. This tutorial shows how to calculate it manually with ATK (without the plugin): http://docs.quantumwise.com/tutorials/thermoelectrics_cnt_isotope.html#thermoelectrics-cnt-isotope

2) The electronic temperature in the Calculator Settings is only used for getting the DFT calculation to converge. It is not a "real" temperature" but rather a smearing of the distribution of electronic occupations around the Fermi level. It is therefore something very different from the temperatures given in the Thermoelectric Coefficients plugin. Use the first method you mention: Only change the temperature in the Thermoelectric Coefficients plugin.

[wot19920302]

1) Please have a look through the literature on thermoelectrics to understand the meaning of the ZT "figure of merit", or simply browse through the wikipedia entry on the subject: https://en.wikipedia.org/wiki/Thermoelectric_materials#Materials_selection_criteria. The ZT is a dimensionless number that indicates the ability of a given material to efficiently produce thermoelectric power. ZT should therefore be as high as possible. This tutorial shows how to calculate it manually with ATK (without the plugin): http://docs.quantumwise.com/tutorials/thermoelectrics_cnt_isotope.html#thermoelectrics-cnt-isotope

2) The electronic temperature in the Calculator Settings is only used for getting the DFT calculation to converge. It is not a "real" temperature" but rather a smearing of the distribution of electronic occupations around the Fermi level. It is therefore something very different from the temperatures given in the Thermoelectric Coefficients plugin. Use the first method you mention: Only change the temperature in the Thermoelectric Coefficients plugin.

Does it mean that "elecrode temperature" in the calculator setting also couldn't affect electronic transmisson spetrum when calculating electronic conductance、seebeck coefficient in various temperature?

[Jess Wellendorff]

Yes, the electronic temperature should not affect electronic transmission spectra, provided you do set it to something excessively high, like 10000 K.

[wot19920302]

thanks for your help!