Calculate effective masses of electron, hole, and exciton from band structure

How to use:

Calculate nscf with Quantum Espresso using 4 k-points:

K_POINTS tripa
 4
 0.0    0.0    0.0    1.
 0.02   0.     0.     1.
 0.     0.02   0.     1.
 0.     0.     0.02   1.

and select necessary bands for study.