Is there a workaround?

The problem is quite fundamental, because in order to get the Fock operator at a certain k-point you need the wavefunctions on a grid that is commensurate with it, this can only be done self-consistently.

However, there are a few things you can do.

1. I think you can add k-points to the scf calculation with weight zero, this is boring (you'll have to specify he grid and the path by hand) and very computationally expensive.

2. you can interpolate the Fock operator, this should be possible if it is expressed om a basis of localized wavrfunctions. There is some development in this direction, but I don't know if it has been implemented already by someone.

3. You could interpolate the wavefunctions, from Wannier functions. This is probably impossible in practice.

4. You can interpolate the Hamiltonian, passing through a Wannier basis representation. This is possible, I have done it, and I've put an example in the git developement branch (PP/examples/W90_open_grid_example/). But you need to know, or learn, how to use Wannier90 (which is a useful skill regardless), and to use the developement version of qe.

kind regards

Stefan Seidl

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Lorenzo Paulatto - Paris
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