[QE-users] question about last steps of vc-relax

[Paolo Giannozzi]

On 9/4/23 11:09, Konstantin Glazyrin wrote:

> An example - target relaxation pressure 600 kbar:
> 1 - total   stress  (Ry/bohr**3)                   (kbar)     P=     
>   600.65 - last run of structure relaxation
> 2 - total   stress  (Ry/bohr**3)                   (kbar)     P=     
>   484.28 - final scf run
> May I ask - what does it indicate

it indicates that your kinetic cutoff is too low for a good description 
of the pressure

> which value I should trust more and how should I proceed?

the former is the pressure, computed for the plane-wave basis set of the 
INITIAL unit cell.
The latter is the pressure, computed for the plane-wave basis set of the 
FINAL unit cell.
They should converge to the same value at sufficiently high cutoff.

> Is it because of this?
> SCF correction compared to forces is large: reduce conv_thr to get 
> better values
> For me it is conv_thr =   6.4000000000d-06

it is a bit too large, but it is hardly related to the original problem

Paolo

> Thank you!
> best wishes,
>              Konstantin
> 
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Paolo Giannozzi, Dip. Scienze Matematiche Informatiche e Fisiche,
Univ. Udine, via delle Scienze 208, 33100 Udine, Italy
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