Some convergence problems

[WEIW]

Dear Daniele,
I am calculating the band structure of monolayer MoS2, and I have some questions to ask.
(1)I found that the calculation would become very slow after adding SOC, so whether the convergence test could be conducted without adding SOC. These measured parameters are then applied to the system with SOC.
(2)After the HF calculation, I found in the report file that the system without SOC was an indirect band-gap semiconductor (in fact, single-layer MoS2 was a direct band-gap semiconductor), and the minimum value of the direct band-gap of the system with SOC was equal to the minimum value of the indirect band-gap. I didn't know what the problem was.
(3)Finally, there was an error when I calculated GW-PPA. Could you please help me to find out what the problem is?
[ERROR] STOP signal received while in :[06] Dipoles

[ERROR] File ./2D_WR_WC//ndb.dipoles; Variable NOT DEFINED; NetCDF: HDF error
I have uploaded three attachments, there are two for the second question and one for the third question.

Best,
LIU

[Daniele Varsano]

Dear Liu,

*please note that without SO you have an indirect gap already ad DFT level, this is because VBM at K and Gamma are nearly degenerate and the gamma VBM energy is slightly larger. I do not know if this an expected results, you can check the literature and eventually fine tuning your scf QE calculation.

* You are using psuedopotential with NLCC, this is discouraged as some inconsistencies arise as they are included in the Vxc but not in the HF part (same reason why it is discouraged in QE for hybrid calculations). You can find oncvpsp psuedo without non linear core corrections at: http://www.quantum-simulation.org/potentials/sg15_oncv/


*About the error in dipoles it is not straightforward to understand the reason. My suggestion is to update to the last version of the code 5.0 and see if the problem persists. You can download the last snapshot of the code at:

Code: Select all

git clone git@github.com:yambo-code/yambo.git yambo

*Note that in the r-HF-no soc you have weird orthonormalisation:

Code: Select all

 [WF-HF/Rho loader] Normalization (few states)  min/max  : 10.00000  -1.00000

as above, try the new version of the code and see if the problem persists.

*Note that in your HF calculation with SOC you did not include the coulomb cutoff. I can also see that the HF terms are not calculated but read from a previous calculation, that it is probably ok, but just to be aware.

*Finally I suggest you to use a larger box side in the cutoff coulomb cutoff e.g. zcut=48 a.u.

Best,
Daniele