GW convergence calculation

GW, Bethe-Salpeter …

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Newlife1982
Posts: 37
Joined: Thu Jun 24, 2010 2:13 pm

GW convergence calculation

Post by Newlife1982 » Sun Jan 16, 2011 5:17 pm

Dear All,

I am calculating the band gap of TiO2 bulk. For the 1×1×1 unit cell, I do the convergence calculations to get the suitable K-point, ecut and so on.
My question is whether I can use these converged parameters to calculate the 2×2×2 unit cell. Should I also do the convergence calculations for the 2×2×2 unit cell. It would be very nice if you could give me some suggestions! Thank you in advance!

Best,

Wang

tetermp
Posts: 4
Joined: Thu Mar 10, 2011 7:16 pm

Re: GW convergence calculation

Post by tetermp » Thu Mar 10, 2011 9:35 pm

Ecut is determined by the ions and not the size of the cell, so your converged value of ecut should be fine for the larger
calculation. The good news is that you can probably lower the number of k-points for the larger cell.
Dr. Michael Teter
1052 Glade Park East
Kittanning, PA 16201

david.waroquiers
Posts: 138
Joined: Sat Aug 15, 2009 12:45 am

Re: GW convergence calculation

Post by david.waroquiers » Fri Mar 11, 2011 11:09 am

Hello,

Your cutoff energies should stay the same (ecut, ecuteps ecutsigx), your k-point grid might be reduced as tetermp mentioned. Concerning the number of bands in the screening and sigma, it should be somewhat linear with the size of the system, so multiplied by 8 in your case.

David

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