Yambo Community Forum

Dear all:
I want to get quasiparticle energies of some specific K points. But I don't know how to input the K points into input file.
For example, I try to calculate quasiparticle energies of (0.4, 0, 0.4) of Si, with 5*5*5 K points generation in BZ, and no-shifted. I think (0.4, 0, 0.4) is included in BZ Q-points (125), but not included in IBZ Q-points.

Thanks

Tieyu Lu

Dear Tieyu Lu,

this is indeed a tricky point. Yambo requires as input a uniform k-grid {k_i}. This is contracted in the IBZ resulting in a certain number of k-points that are printed in any report file. Now starting from grid Yambo generates the corresponding grid of transferred momenta {q_j}. You can calculate QP corrections for

• any k-point in the grid {k_i} (in the IBZ)
• any k-point of the BZ that is obtained by rotating a k-point of the grid {k_i}. In this case the QP correction is the same of original, un-rotated point, for symmetry reasons.

If you need to calculate QP corrections for a k-point that is not included in the grid {k_i} or obtained with a rotation than you need to perform a more elaborate procedure using simultaneously 2 grids. Yambo can do it but the procedure is more complicated. Is this your case ?

Andrea

Dear Lu,

If the special point is included in the BZ, there must be an equivalent point in the IBZ. If not, why do we call it IBZ?

To find out the equivalent point, I plot all the points in the BZ and IBZ. Based on the symmetry of BZ, it is easier to spot that equivalent point.

Sincerely,