"Stencil order" / "Delta" @ "Effective Mass" calculation

[Dipankar Saha]

I had a few questions regarding the 'effective mass' that we obtain from the "Effective Mass" analyzer.

1) Is this good for the parabolic bands only? (or, it can capture any band dispersion through empirical fittings...)
2) What are those "Stencil order", and "Delta" values signify?

Thanks and Regards_
Dipankar

[Jess Wellendorff]

You can in principle use the EffectiveMass analysis to compute the effective mass in any band at any k-point, but effective masses in the VBM and CBM are usually of most interest. The method uses a finite-difference method to determine the second-order derivative of the band energy wrt. k. The stencil order sets the number of points used in fitting, while Delta sets the distance between the points. The upcoming ATK 2016 will contain a more elaborate documentation of the EffectiveMass analysis object.

[Dipankar Saha]

Okay..../ Thank you Jess ....