[QE-users] Question rgd. q grid for HSE calculations

[Shivesh Sivakumar]

Hello users,

I was seeking a clarification in the documentation for calculation of the
exact exchange in HSE calculations. Paraphrasing what's mentioned in the
documentation:

Specifically, in the case of large non-metallic systems, it is reasonable
that NQS can be set to 1 (where NQS = nqx1*nqx2*nqx3).

My qualms are:
1. I wonder how loose the definition of 'large non-metallic systems' is.
Does it just stipulate a large enough bandgap? (Even though KS-DFT
underestimates it?)
2. Why does the nature of the system allow us to adopt a very coarse q grid?

I would greatly appreciate any inputs on these points.


Sincerely,
Shivesh Sivakumar
Graduate Teaching Assistant
Materials Science and Engineering
University of Washington-Seattle
WA-98105
(206) 474-8174
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