[QE-users] Choosing convergence criteria for vc-relax

[Appleton, Robert J]

Hello,

I am trying to study the phonons of the material BaZrS3 to determine if it is stable for a given structure. I first use phonopy and vasp and found negative frequency values for phoning band structure. My advisor is concerned in the optimization of the structure and so we now want to use quantum espresso. I have only used it a few times and mostly used default or example inputs. The input I want to make sure is sufficient is my criteria for convergence.

Under the &control:
force convergence criteria right now is
forc_conv_thr = .0001 <— this value seems to big but how do I choose a value that is best for optimization but does not take to much computer time?

Under the &electrons:
conv_thr = 1.d-9 <— I am considering changing to 1.d-12. Is this a good idea?

Under &system:
I am using ecutrho = 12 • ecutwfc

If you can give me some advice on how best to choose convergence criteria for studying phonons that would be very good thanks.

Robert Appleton
Cal State LA - MS Physics Student

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