[QE-users] Accuracy conduction bands

[Lun Yue]

Hi QE experts,

For my project I will need momentum matrix elements between valence and 
high-lying conduction bands. For MgO, using bands.x, I was able to 
calculate the momentum matrix elements p_mn. The problem is that the 
magnitude |p_mn| between a valence band and a high-lying conduction band 
(e.g. the 50th conduction band), is of the same order of magnitude as 
|p_mn| for lower conduction bands. I was wondering whether this is 
physical? Or are the high-lying conduction bands calculated with bad 
numerical accuracy such that p_mn is not sensible to calculate?

Best regards,

Lun Yue

Lousiana State University