low symmetry and Gamma-point

[Mohammad Alidoosti]

Dear Yambo developers,
I am trying to calculate the optical properties of some 2D structures. Due to the need of getting some information in a specific direction, I want to run nscf.in in the nonequal mesh (e.g. 8 4 1). During initialization, r_setup encompasses such a qmesh, whereas, in the next step (yambo -o -k Hartree) yambo.in is restricted by $\Gamma$ point (% QpntsRXd 1 | 1 |). I found that such a problem arise from the low symmetry embedded in my crystal structure. Could you please guide me to overcome this problem?

Best,
Mohammad

[Daniele Varsano]

Dear Mohammad,
please sign your post with your affiliation, this is a rule of the forum and you can do once for all filling the signature in the user profile.
The problem is due to the fact the yambo sees 2 equivalent points in the rlu q-grid

Code: Select all

[WARNING][RL indx] 2 equivalent points in the rlu grid found
 [RL indx] X grid is not uniform. Gamma point only.

You can try to delete your ./SAVE/ndb* files and rerun the setup uncommenting the keyword NoDiagSC in the input file. (you can generate the file using yambo -i -V all)

Best,
Daniele

[Mohammad Alidoosti]

Dear Daniele,
Thanks for your reply. After applying your advice, the problem remains unsolved. That is, the following line is displayed in the r_setup:

"[RL indx] Q BZ pts are /= from X grid BS pts. Gamma point only."

Best,
Mohammad

[Daniele Varsano]

Dear Mohammad,
can you post the r_setup and input files?

Before that can you try the following:
*delete all the ./SAVE/ndb.* files
*edit an input file containing only:

setup
NoDiagSC

*run the code

Best,

Daniele

[Mohammad Alidoosti]

Dear Daniele,
Solved. I am grateful for your help.

Best,
Mohammad

[Daniele Varsano]

Great,

we have two algorithms to setup the q grid. The default one sometimes fails when dealing with non-orthorhombic cells e.g. hexagonal lattice, the second one is activated with the keyword NoDiagSC. Probably we should change the default in the future.

Best,

Daniele