Yambo Community Forum

Dear all:
1、When I calculate the GW-BSE collision step, I always encounter a memory overflow issue. Then I used 100 CPUs and set up There was an error as follows: Then I changed the settings of the CPUs, When the task is calculated to [06.01] SEX+HARTREE (e-e correlation) this step, the process will be stuck. Could you kindly advise on how we might allocate CPU resources more effectively in such scenarios? I appreciate any guidance and tutorial on that!


2、While calculating the two-dimensional material, I observed that the second harmonic generation (SHG) output in the z-direction (Xz**) is showing no value. However, based on the material's symmetry, I would expect it to have a non-zero value. Could you please help clarify why this might be the case?Thank you for your assistance!

Best，
sunxl

Dear sunxl

1) regarding the collisions
*) I advise you to try with a small k-points sampling at the beginning and then increase it
*) use yambo_rt to calculate the collisions because it is in single-precision and it requires half of the memory and it is faster, then you can perform non-linear reponse with yambo_nl
*)You can also try this approximated collisions:
https://wiki.yambo-code.eu/wiki/index.p ... r_response
but you have to check if this approximation is good for your system, just do linear response and compare with standard BSE


2) Since the non-linear response code is based on dynamical Berry phase, non periodic directions are not implemented.
So you are right the SHG in z-direction is not zero but you cannot calculate it with Yambo at present

best
Claudio

Dear sunxl,

just an addendum to the suggestions from Claudio.

After the interrupted runs of your log files, yambo will leave inside your "03_coll" folder the files "ndb.em1s*"

Those are fine. Just keep them and re-run the code. Yambo will skip the (long) step and, instead, it will load the screening from the "ndb.em1s*" files and directly start the computation of the collisions.

Best,
D.

P.S.: please add the signature to your user profile, it is a rele of the forum

Dear claudio and Davide,

Thank you for your suggestions!

Additionally, I also conducted a test. For the two-dimensional material, I set the k-point in the z-direction to 2, which allowed me to obtain the SHG component Xz**output in the z-direction. Could you please confirm if the results obtained this way are correct?

Best.
sunxl