On 2017-08-28 11:40, Lorenzo Paulatto wrote: > 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, [email protected] 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 >> _______________________________________________ >> Pw_forum mailing list >> [email protected] >> http://pwscf.org/mailman/listinfo/pw_forum
Dear Lorenzo, thank you for your kind attention. I checked the total energy of the system and it keeps decreasing. However, there is another ambiguous point in the results. In fact, as our system is a sheet and we set 15 Angstrom distance between subsequent layers in z-direction, I expect that the z-components of atomic positions do not change during relation process. But after a couple of relation steps this happens. To me it doesn't seem normal!!!! regards, Leila Eslami Department of physics, Islamic Azad University, Tehran, Iran _______________________________________________ Pw_forum mailing list [email protected] http://pwscf.org/mailman/listinfo/pw_forum
