EPW Forum

Dear EPW users,

I find that the electron linewidth, comprising of both long-range and short-range terms, for equivalent k-points are not exactly the same. Sometimes, the difference can reach 50% in my calculation of a polar material- zinc blende GaAs. For example, the linewidth at (0, 0.02, 0) in crystal coordinate is ~1.2 meV which is lower than the value (~ 2.4 meV) at other degenerate points e. g., (0.02, 0, 0). I also checked that the energy and velocity at these points which are very close.

Should degenerate kpoints have the same linewidth? Have EPW averaged the values for degenerate points? Thank you for your help!
p.s. I use gamma-centered k- and q-meshes.

Tianshi Wang
Graduate student, University of Delaware

Dear Tianshi Wang,

Observable should indeed be the same for symmetry equivalent k-points.

However, due to numerical accuracies, it is not exactly true. It should be close if you are converged.

No average is performed on the k-points. However, for each k-point an average is made for the linewidths on degenerate bands.

The energies and velocities should be exactly the same (at least to a lot of digit). If not, you might want to raise ecut, coarse k-grid and check that your
Wannier interpolation is correct (i.e. that the Wannier interpolation respect the symmetry of your crystal).

Best,
Samuel

Dear Samuel,

Thank you for your reply! I will check the convergence.

Best
Tianshi