# Effective Mass¶

EffectiveMass
Enabled [True | False]
KPointCoord float_list
NumAbove integer
NumBelow integer
StepSize float
End

EffectiveMass
Type: Block In a semi-conductor, the mobility of electrons and holes is related to the curvature of the bands at the top of the valence band and the bottom of the conduction band. With the effective mass option, this curvature is obtained by numerical differentiation. The estimation is done with the specified step size, and twice the specified step size, and both results are printed to give a hint on the accuracy. The easiest way to use this key is to enabled it without specifying any extra options.
Enabled
Type: Bool False Compute the EffectiveMass.
KPointCoord
Type: Float List 1/Bohr True Coordinate of the k-points for which you would like to compute the effective mass.
NumAbove
Type: Integer 1 Number of bands to take into account above the Fermi level.
NumBelow
Type: Integer 1 Number of bands to take into account below the Fermi level.
StepSize
Type: Float 0.001 Size of the step taken in reciprocal space to perform the numerical differentiation