  Heusler-type Fe2VAl compound is a promising thermoelectric candidate with
non-magnetic ground state. The present work investigates the Seebeck
coefficient (S) of Fe2VAl in the temperature region 300 to 620 K with the help
of experimental and theoretical tools. The experimental value of S is observed
-130 {\mu}V/K at 300 K. Afterthat, the magnitude of S decreases gradually as
the temperature increases. At T = 620 K, the value of S is found to be -26
{\mu}V/K. In order to understand the behaviour of the experimentally observed S
value, the band-structure and density of states calculations are performed by
using LDA, PBE, PBEsol, mBJ and SCAN within density functional theory. All the
above mentioned exchange-correlation (XC) functionals (except mBJ) predict the
semi-metal like behaviour of the compound, whereas the mBJ gives the indirect
band gap of 0.22 eV having the well agreement with experimentally observed
value. The temperature dependence of S for Fe2VAl is also calculated with the
help of all the five mentioned functionals individually. The best XC functional
is investigated for searching the new thermoelectric materials by taking Fe2VAl
as a case example through this study. The best matching between experimental
and calculated values of S as a function of temperature is observed by setting
the mBJ band gap with the band-structure of PBEsol or SCAN. Therefore, the
present study suggests that the band-structure of PBEsol or SCAN with mBJ band
gap can be used for searching the new thermoelectric materials.
