[QE-developers] Reproducibility of results in quantum espresso

[Lorenzo Paulatto]

Dear Mohd,
variable cell optimization is done at fixed number of plane waves, not at fixed cutoff. If your initial cell is not far away from the equilibrium, and if your cutoff is tight enough, this won't make much difference, but possibly this was not your case. Check the FFt grid size in output of the first and second calculation, and you will probably remark large differences.

kind regards
LP (CRNS, SU)

Lorenzo Paulatto - Paris
On Mar 19 2022, at 5:46 pm, Mohd Riyaz <riyazpu at gmail.com> wrote:
> Hi
> I am doing an adsorption study, what happen was that the number of optimization steps exceed 100 so the calculation stoped and the energy value for last step was -3449.81437 Ry. I copied the cell parameters and the atomic coordinates from the last step in the output file and past it in the same input and rerun the calculation. But the energy value after first scf convergence is much higher (-3449.10281 Ry) as compare to the value from previously stope calculation, although both the geometry are the same. In fact the energy after full optimization was 3449.41283 Ry which also lower than non-optimized geometry. If anyone can give a suggestion why is this happening?
>
> Thanku
>
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