link

http://link.springer.com/article/10.1007/s12648-014-0552-0

www.sitelinks.info/nspt.org/

http://worldwidescience.org/topicpages/h/hopping+conduction+mechanism.html

https://www.chemweb.com/articles/00092614/0637000C

Dear Jaydeep,

if I should help you, you have to explain to me what is NSPT equation. In the usual simple case of small  polaron hopping at the "Fermi level", you do not really need to know the position of the Fermi level (properly electrochemical potential !!). You just calculate a single small polaron hopping rate and then multiply this by the concentration of polaronic carriers and some other constants. The matter is different if the carriers that self-trap are positioned in energy away from the electrochemical potential. The decay parameter alpha is one of the free fitting parameters, but is usually equal to interatomic distance.

You might also consult  Phys.Rev. B28(2) (1983), 927.

i hope this helps

With best regards

Petr