[Pw_forum] problem in vc-relax convergence

Lorenzo Paulatto lorenzo.paulatto at impmc.upmc.fr
Mon Aug 28 09:10:04 CEST 2017

Dear Leila,

if the total energy keeps decreasing, that it is completely normal: it 
means that you started from an energy saddle point. It may however 
indicate that your initial crystal structure was wrong.

kind regards

On 28/08/17 07:22, l.eslami at srbiau.ac.ir wrote:
> Hi all,
> We are trying to perform vc-relax calculation for a single layer ZnO
> sheet in the presence of an oxygen vacancy in a 4*4 suppercell. We have
> used espresso-5.4.0. with different psudopotentials such as GGA,
> NORMCONS and non relativistic Pseudopotentials: "O.pbe-mt_fhi.upf and
> Zn.pbe-mt_fhi.upf,  as well as GBRV pseudopotentials:
> “o_pbe_v1.2.uspp.F.UPF” and “zn_pbe_v1.uspp.F.UPF”. The calculations do
> not return any error. However, convergences of force and pressure do not
> occur even after long time running of the calculations. In fact, the
> code starts to decrease force and pressure but after a couple of
> relaxation steps they increase. I would be grateful if anyone could
> kindly give me any piece of advice to solve the problem.
> many thanks,
> Leila Eslami
> Department of physics,
> Islamic Azad University,
> Tehran, Iran
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Dr. Lorenzo Paulatto
IdR @ IMPMC -- CNRS & Université Paris 6
phone: +33 (0)1 442 79822 / skype: paulatz
www:   http://www-int.impmc.upmc.fr/~paulatto/
mail:  23-24/423 Boîte courrier 115, 4 place Jussieu 75252 Paris Cédex 05

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