[QE-developers] issues with nrX and vc-relax calculation

[Lorenzo Paulatto]

Hello,
I'm just writing here instead of opening an nth issue on gitlab. As I 
have some questions and no solution.

I've noticed that when doing a vc-relax calculation, even if nr1, nr2, 
nr3 are fixed from input the final calculation after convergence is done 
with the cutoff grid, i.e. the values of nr1, nr2 nr3 are ignored.

I think this is a source of troubles, i.e. because if you follow up the 
pw calculation with something else you may not notice that the grid has 
changed and run into troubles. Also, note that there are some cases 
where it is not completely stupid to fix nrX with a variable cell, i.e. 
when using cell_dofree="shape"

I think on possible solution would be to skip the last calculation 
completely if any nrX is set from input: we can assume that if the user 
did this she know why and want to keep the grid fixed.

Or, we can do the final calculation with the initial nrX, although I 
think it becomes completely useless?

Or keep everything as it is, which also has some advantages, but maybe 
introduce an input flag (yes) to skip the final calculation.

cheers
-- 
Lorenzo Paulatto - Paris