Momentum density of silicon valence band using bandstructure

[Samisdabes]

TL;DR

I am attempting to use python to calculate the gradient of the bandstructure for the 3 bands in the valence band for a bandstructure, at a discrete set of points and then plot them in a histogram to get the electron momentum density curve. However I have problems.

I have included the resulting histogram that emerges when I do this procedure and it does not look as expected. I am using CASTEP and have read the .bands file as a txt file into python where i have extracted the relevant data.

 

[Dr Transport]

Why do you need the gradients? Your plot doesn't really make any sense to me.

 

[Phil Hasnip]

You don't give us enough information to interpret your plot. However, if you want the band-gradients in momentum space then they are basically the optical matrix elements, so just ask CASTEP for them:

task : spectral
spectral_task : optics

and then make sure your spectral_kpoints_list has the k-points you want.