[Pw_forum] Negative stress(vacuum) in vc-relax's last scf

[Bahadir Altintas]

hi,

I am getting negative stress around -500 Kbar for the SCF procedure at the end
for the vc-relax. is it normal or should it be 0.00 Kbar? For bfgs steps, it
converges around 0.01 Kbar but last scf shows -500Kbar  total stress. ewald is
the same for latest bfgs and scf.  I am confused. any explaination?
I use QE 4.3.2 fhi.UPF(converted from abinit LDA_FHI pseudpotentials using
fhi2upf), ecutwfc is 45 Ry and K-mesh is 8 8 8 automatic.
i think convvergence thresholds are enough as D-12 for energy D-8 for forces.

thank you


Bahadir Altintas, PhD
Department of Chemistry(Visiting Scholar)

335 NATURAL SCIENCES COMPLEX
UNIVERSITY AT BUFFALO
STATE UNIVERSITY OF NEW YORK