I've read in some texts that GW-BSE quasiparticle calculations have only been implemented on Norm-conserving Pseudopotentials (and not Ultra-soft or PAW PPs). Is there a conceptual reason for this? I can't seem to locate a reliable source but here it is mentioned that the YAMBO code (used for GW-BSE in conjunction with Quantum Espresso) can only support NCPPs.

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    $\begingroup$ I don't have a detailed answer, but it's not uncommon for certain calculations to only support NCPP at first, since the implementation is usually much simpler. For example, all meta-GGA in QE only support NCPP. Even hybrid functionals were only NCPP until a few years ago. I would say that now this is less of a handicap, there are some excellent NCPPs at pseudo-dojo.org and from the SG-15 set (quantum-simulation.org/potentials/sg15_oncv). $\endgroup$ – Kevin J. M. May 31 '20 at 19:31
  • $\begingroup$ @KevinJ.M. Thanks. I thought there was some conceptual basis. Your answer on ease of implementation at the beginning makes total sense.. $\endgroup$ – livars98 May 31 '20 at 19:38
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    $\begingroup$ @livars98 I have re-phrased the question and it has also been posted on Twitter: twitter.com/StackMatter/status/1270128384664842240, so hopefully it will get an answer now. What evidence do you have that they can only be run on NCPPs though? If none, then Kevin's answer that using NCPPs just makes implementation easier, might be correct. $\endgroup$ – Nike Dattani Jun 8 '20 at 23:02
  • $\begingroup$ great, agreed @NikeDattani $\endgroup$ – livars98 Jun 9 '20 at 3:28
  • $\begingroup$ @livars98 "I've read in some texts that GW-BSE quasiparticle calculations can run on only NCPPs" ... which texts are these? Can you please show us? $\endgroup$ – Nike Dattani Jun 9 '20 at 3:34

The GPAW code can do GW/BSE and it uses purely PAW potentials. So it's absolutely possible to do GW/BSE with PAW sets. The involvement for the implementation, however, is another topic. From Kevin J. M.'s answer, the primary block is fairly clear: PAWs are quite involved to implement. Doing all of the atom-centered corrections and then getting them onto your regular grid requires a focused effort to do, and is perhaps not the highest priority of many codes out there (somewhat understandably so, but PAW does allow very low PW cutoffs...).

In case you're interested, the tutorials for GW/BSE in the GPAW code are as follows:

  1. GW
  2. BSE

I'm fairly confident that Abinit also supports PAW potentials + GW/BSE as well. I think the key point is always how much the PAW methodology is prioritized by the code's developers.

  • $\begingroup$ +10. Great answer? $\endgroup$ – Nike Dattani Jun 9 '20 at 15:27

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