GW correction on large isolated system

[el16yz]

Dear Yambo users,

I am using Yambo 4.5.1 to perform GW correction on a large isolated system. The parallel calculation is applied for speeding up the process: 64 cores, 25G/core. The calculation keeps running 48 hs but doesn't finish. And there is not any new update in log files since 2 hours from calculation begin. From the report file, it seems that the process is trapped in the calculation of Dynamic Dielectric Matrix. The input, report, and log files are submitted as attachments. It will be very appreciated if you can check and solve my problem. Thank you.

Best,
Yang

[claudio]

Dear Yang

I don't know why your calculation got stuck, anyway I give
some suggestions.

1) Use fewer processors for linear algebra, for example
X_nCPU_LinAlg_INV= 16

2) try to use a lower cutoff for the dielectric constant
NGsBlkXp= 5000 mHa # [Xp] Response block size

3) in the polarization you should put all the bands
1 | 400 | # [Xp] Polarization function bands

4) try to parallelization mode "memory"
PAR_def_mode= "memory"

and check if it works
best
Claudio

[el16yz]

Dear Claudio,

Thanks for your suggestions.

2) try to use a lower cutoff for the dielectric constant
NGsBlkXp= 5000 mHa # [Xp] Response block size

I have tried to set NGsBlkXp= 1 Ry before. It can produce a result in a few minutes. But the result is an unexpected one, which may be due to convergence issues. Hence, I need to keep increasing NGsBlkXp until the result catches convergence. But the problem occurs when I increase it to 4 Ry. What is the possible reason for that?

Best,
Yamh

[el16yz]

Dear Claudio,

Thanks for your suggestions.

2) try to use a lower cutoff for the dielectric constant
NGsBlkXp= 5000 mHa # [Xp] Response block size

I have tried to set NGsBlkXp= 1 Ry before. It can produce a result in a few minutes. But the result is an unexpected one, which may be due to convergence issues. Hence, I need to keep increasing NGsBlkXp until the result catches convergence. But the problem occurs when I increase it to 4 Ry. What is the possible reason for that?

Best,
Yang

[claudio]

Dear Yang

GW convergence of isolated systems can be quite complicated.
First of all keep NGsBlkXp= 5000 mHa, this value is usually enough large
to have converged results.

Then you have to number of bands in the G and W. I think 400 is a small number,
you should have something of the order of 1000 or 2000 bands.

Then you have to consider the size of the supercell, that should be
large at least double of your cluster or molecule,
and then you should use a cutoff to reduce the interaction with the neighbor replica,
you can activate it with the flag "-r".


Have a look here:
http://www.yambo-code.org/wiki/index.ph ... rial:_h-BN
http://www.attaccalite.com/yambo-input- ... explained/
http://www.attaccalite.com/reasonable-p ... culations/

best
Claudio