[Wannier] Analysing BoltzWann outputs

[Bang C. Huynh]

Dear all, 

I am having a few questions regarding how to analyse the outputs of
BoltzWann correctly. 

1. When the thermoelectric results are calculated over a range of
chemical potentials, at what value of chemical potential should I pick
out the thermoelectric properties such that they are reasonably closest
to the real physical properties of the system? Is this in any way
related to the Fermi level calculated by the nscf calculation by QE? I
haven't obtained any experimental data yet and I am trying to use
BoltzWann to help guide my syntheses, so I would like to get as much
meaningful physical insights from these calculations as possible. 

2. How should I treat the effect of anisotropy as BoltzWann outputs the
thermoelectric properties as tensors where, in most, if not all, cases,
the xx, yy and zz components are not identical / vastly different. I
think anisotropy only applies to single crystals, and my system consists
of polycrystalline grains, so some averaging must have taken place in
reality to result in apparent isotropy. But I am not sure how to process
BoltzWann data to take into account this averaging. My ultimate goal is
to investigate how the figure of merit ZT varies with temperature, so
perhaps I will need to average the Seebeck coefficient, electrical
conductivity and thermal conductivity. 

My apology of these questions seem elementary, as I have not had much
experience with solid-state physics/chemistry. I really look forward to
your reply. 

Thank you very much. 

Regards, 
-- 

BANG C. HUYNH
Peterhouse
University of Cambridge
CB2 1RD
The United Kingdom
 
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