Ok That does make sense! Also, today I performed the same calculations with Gaussian 09 and 3G-STO basis and found the same weird landscape and very close local minima/energies which further confirms what you just said. So based on that, my system has a loose ZrOSi angle and the energy changes become visible only when I make the angle very tight...
Thanks for your help. Arash On 2017-04-19 21:02, stefano de gironcoli wrote: > then the relaxation found a local minimum which is all it is guaranteed > to find and by exploring the angular dependence you found a better > minimum or at least a configuration oh lower energy. If the other > coordinates were not optimized, starting the relaxation from this > configuration should lead to a better (local) minimum. > I have no idea whether the 5 mRy=70meV barrier is real or an artifact > of > a noisy landscape due to low cutoff/k-points . > > stefano > > > On 19/04/2017 20:16, sarashs wrote: >> Yes! there is a tiny barrier of 0.005 Ry >> >> Arash >> >> On 2017-04-19 00:20, Stefano de Gironcoli wrote: >>> Is there an energy barrier between the minimum found by relax and the >>> one you find varying the angle ? >>> >>> stefano >>> (sent from my phone) >>> >>>> On 18 Apr 2017, at 21:54, sarashs <[email protected]> wrote: >>>> >>>> They use exactly the same cuttoffs, K-points and everything >>>> (unfortunately.) but the near equilibrium energies are slightly less >>>> than equilibrium one. For instance for SiOZr angle at equilibrium I >>>> get: >>>> >>>> ! total energy = -245.22924923 Ry >>>> Harris-Foulkes estimate = -245.22924923 Ry >>>> estimated scf accuracy < 3.9E-12 Ry >>>> >>>> The total energy is the sum of the following terms: >>>> >>>> one-electron contribution = -715.79581276 Ry >>>> hartree contribution = 369.08543112 Ry >>>> xc contribution = -57.16353294 Ry >>>> ewald contribution = 158.66552815 Ry >>>> Dispersion Correction = -0.02086281 Ry >>>> >>>> And for SiOZr angle at equiliberium-25 I get: >>>> >>>> ! total energy = -245.23454839 Ry >>>> Harris-Foulkes estimate = -245.23454839 Ry >>>> estimated scf accuracy < 1.7E-12 Ry >>>> >>>> The total energy is the sum of the following terms: >>>> >>>> one-electron contribution = -739.45020087 Ry >>>> hartree contribution = 380.81843421 Ry >>>> xc contribution = -57.19470926 Ry >>>> ewald contribution = 170.61520075 Ry >>>> Dispersion Correction = -0.02327322 Ry >>>> >>>> Which is similar in terms of total energy but slightly lower and >>>> that's >>>> weird. Is there anything I can do to force QE to use the same basis >>>> set >>>> throughout SCF calculations? >>>> >>>> >>>>>> On Tuesday, 18 April 2017 17:10:25 CEST sarashs wrote: >>>>>> the other SCF's not have higher energy than the >>>>>> equilibrium angle regardless of them being optimized with a >>>>>> constraint? >>>>>> I mean if the structure is originally relax (which it is) then one >>>>>> expects other near equilibrium structures to have higher energies. >>>>>> Am >>>>>> I >>>>>> wrong there? >>>>> You are right. >>>>> >>>>> They should be higher, which usually means less negative. As long >>>>> as >>>>> the same >>>>> pseudopotentials, cutoffs, k-points and everything else is used. >>>>> >>>>> Do they? >>>> _______________________________________________ >>>> Pw_forum mailing list >>>> [email protected] >>>> http://pwscf.org/mailman/listinfo/pw_forum >>> >>> _______________________________________________ >>> Pw_forum mailing list >>> [email protected] >>> http://pwscf.org/mailman/listinfo/pw_forum >> _______________________________________________ >> Pw_forum mailing list >> [email protected] >> http://pwscf.org/mailman/listinfo/pw_forum > > > _______________________________________________ > Pw_forum mailing list > [email protected] > http://pwscf.org/mailman/listinfo/pw_forum _______________________________________________ Pw_forum mailing list [email protected] http://pwscf.org/mailman/listinfo/pw_forum
