DFT+U

[Ahmad Nabi]

Dear BGW developers, when doing a GW calculation on top of a DFT+U calculation how does one ensure that there is no double counting in Sigma. Does sigma read the matrix elements of the Hubbard potential ( vhub.dat ) file automatically or is there a flag that one needs to input to do that. I am worried that it may not be reading it since I don't see it in the output of sigma calculation. 

Thank you for any advice and help in advance. 

[Fangzhou Zhao]

Dear Ahmad,

You can use the vhub_flag = .true. flag in the pw2bgw.x to output the vhub.dat file, with vhub_diag_nmin and vhub_diag_nmax to set the min and max band index you would like to output. You can subtract vhub term manually from the calculated Sigma, and then there will be no double counting in Sigma. I think currently there is not a flag for vhub in Sigma. Please refer to the SM of Wu et al.  (https://static-content.springer.com/esm/art%3A10.1038%2Fs41467-019-10325-7/MediaObjects/41467_2019_10325_MOESM1_ESM.pdf)  Please feel free to ask us if you have any future questions. Thanks.

Best,

Fangzhou

On Sat, Mar 8, 2025 at 5:29 PM 'Ahmad Nabi' via BerkeleyGW Help <he...@berkeleygw.org> wrote:

Dear BGW developers, when doing a GW calculation on top of a DFT+U calculation how does one ensure that there is no double counting in Sigma. Does sigma read the matrix elements of the Hubbard potential ( vhub.dat ) file automatically or is there a flag that one needs to input to do that. I am worried that it may not be reading it since I don't see it in the output of sigma calculation. 

Thank you for any advice and help in advance. 

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Fangzhou Zhao

Ph.D. 

Department of Physics

University of California, Berkeley