Dear Cyrille, I just made an alteration to add_bfield.f90 only including constraint energy contributions from the magnetic ions. This I expect is an indirect way of setting the lambdas for other atoms to zero albeit not very general.
It's a Fe3+ system which in the high-spin state should have 5 unpaired electrons. While I don't expect to achieve that ideal value (actually I don't when doing a regular unconstrained calculation biased towards the high-spin state) I am only testing the constraint optimisation. Thanks, Vardha. On Sun, Mar 9, 2014 at 2:24 AM, BARRETEAU Cyrille <cyrille.barreteau at cea.fr>wrote: > Dear Vardha > > For the moment in the actual version of pw there is only one lambda which > applies to all types of atoms. > I have no idea of the type of systems you are looking at but a target > moment of 5 for Fe is just "crazy". > So this is not surprising that you need such large values of lambda to > converge towards this solution. > I am even surprised that you managed to get a solution! > > > Cyrille > > > ----------------------------------------------------------------------------------------------------------- > *Cyrille Barreteau* > CEA Saclay, IRAMIS, SPCSI, Bat. 462 > 91191 Gif sur Yvette Cedex, FRANCE > ~~~~~~~~~~~~~~~~~~~~~~~~~~~~ > phone: +33 (0)1 69 08 29 51 / +33 (0)6 47 53 66 52 > fax : +33 (0)1 69 08 84 46 > email: cyrille.barreteau at cea.fr > Web: http://iramis.cea.fr/Pisp/cyrille.barreteau/ > > ----------------------------------------------------------------------------------------------------------- > ------------------------------ > *De :* pw_forum-bounces at pwscf.org [pw_forum-bounces at pwscf.org] de la > part > de Varadharajan Srinivasan [varadharajan.srinivasan at gmail.com] > *Envoy? :* samedi 8 mars 2014 20:02 > > *? :* PWSCF Forum > *Objet :* Re: [Pw_forum] Constrained magnetic calculation > > Dear Cyrille, > > This is what we ended up doing setting all lambdas except the two > magnetic ions to zero. However, the constrained moments still seem to > converge rather slowly with lambda. I attach the plot below. We are also > testing this on a Fe-Cr system. We set the target moments to 5 for Fe and > -3 for Cr (antiferromagnetic arrangement). Is there any physical reason why > this would happen? > > Best, > Vardha > > > On Thu, Mar 6, 2014 at 3:31 PM, BARRETEAU Cyrille < > cyrille.barreteau at cea.fr> wrote: > >> In fact it can be very useful to constrain just some atoms and not all >> of them. We used that option a few years ago when studying the magnetic >> properties of Cr atoms in a Fe matrix. At that time we did it by hacking >> ad_bfield.f90. An alternative solution would be to define a different >> lambda(i) for each type of atom and set lambda(i)=0 for the atom which do >> not need to be constrained. >> >> regards >> Cyrille >> >> >> ----------------------------------------------------------------------------------------------------------- >> *Cyrille Barreteau* >> CEA Saclay, IRAMIS, SPCSI, Bat. 462 >> 91191 Gif sur Yvette Cedex, FRANCE >> ~~~~~~~~~~~~~~~~~~~~~~~~~~~~ >> phone: +33 (0)1 69 08 29 51 / +33 (0)6 47 53 66 52 >> fax : +33 (0)1 69 08 84 46 >> email: cyrille.barreteau at cea.fr >> Web: http://iramis.cea.fr/Pisp/cyrille.barreteau/ >> >> ----------------------------------------------------------------------------------------------------------- >> ------------------------------ >> *De :* pw_forum-bounces at pwscf.org [pw_forum-bounces at pwscf.org] de la >> part de Gabriele Sclauzero [gabriele.sclauzero at mat.ethz.ch] >> *Envoy? :* mercredi 5 mars 2014 10:38 >> *? :* PWSCF Forum >> *Objet :* Re: [Pw_forum] Constrained magnetic calculation >> >> Dear Varadharajan, >> >> I do not know if it make sense or not in general, anyway this >> possibility is not available at the moment. All atoms of atomic type i will >> be constrained to have local magnetization equal to >> starting_magnetization(i). However, you can try to edit the magnetic >> constraint subroutine in PW/src/add_bfield.f90 to suit your needs. >> >> Regards >> >> >> GS >> Materials Theory, ETH Zurich >> >> >> On 03/05/2014 05:25 AM, Varadharajan Srinivasan wrote: >> >> Dear Gabriele, >> >> To add to Paresh's question is it possible (and does it make sense) to >> constrain the magnetisation of only a few atoms and not the others? While >> the target here seems to be atoms 3 and 4 the other atoms are being made to >> pay the price so to speak. >> >> One option, in the present framework, is to constrain the values of >> magnetisation of all other atoms to their respective lambda=0 values. Could >> this speed up the convergence with lambda? >> >> Thanks, >> Vardha. >> >> >> On Tue, Mar 4, 2014 at 7:18 PM, Gabriele Sclauzero < >> gabriele.sclauzero at mat.ethz.ch> wrote: >> >>> >>> What about the evolution of the constrained magnetization? >>> (Please also make sure that the values specified in >>> starting_magnetization make sense, as suggested by L. Paulatto Sir). >>> >>> My suggestion was to vary lambda in small steps (say 0.5). I'm surprised >>> that you managed to converge the calculation with such high lambda values. >>> >>> Anyway, the constrain energy looks way too large, your system is >>> probably still far from the target. >>> >>> >>> GS >>> >>> >>> On 03/04/2014 01:57 PM, paresh rout wrote: >>> >>> Respected Sclauzero sir, >>> Thanks for your reply. According to your suggestion, I varied my >>> Lambda value from 0,5,.......150 ry. Although calculated constrained >>> energy are decreasing but upto 150 ry the constrained energy and the >>> estimated scf accuracy are not the same order. Here I am providing my >>> constrained energy with various lambda value. >>> >>> Lambda Constraint_Energy >>> 0 0.00000000 >>> 5 36.93411685 >>> 10 69.54815816 >>> 15 6.65653915 estimated scf accuracy < 7.6E-13 Ry >>> 20 7.88546052 >>> 25 8.88385707 >>> 30 9.71513061 >>> 35 10.42697250 >>> 40 11.05006563 >>> 45 11.60072229 >>> 50 12.08887057 >>> 70 13.54966033 >>> 80 14.05546257 >>> 90 14.45159513 >>> 100 14.75974550 >>> 110 14.99680383 >>> 120 15.17624003 >>> 130 15.30876396 >>> 140 15.40310437 estimated scf accuracy < >>> 9.9E-13 Ry >>> 150 15.46632278 estimated scf accuracy < >>> 9.9E-13 Ry >>> >>> >>> >>> >>> On Tue, Mar 4, 2014 at 3:06 PM, Sclauzero Gabriele < >>> gabriele.sclauzero at mat.ethz.ch> wrote: >>> >>>> Dear Paresh, >>>> >>>> in my understanding you should start with a very small lambda >>>> value (e.g. 0.1), make sure the calculation has converged (not always >>>> trivial), then restart with a larger value. >>>> It is important to tune the steps by which you increase lambda. >>>> Increasing it by steps of 5 seems too much to me, I would suggest you to >>>> try much smaller steps, say between 0.1 and 0.5. >>>> >>>> There are two reasons why the energy increases: the first is because >>>> you are constraining your system out of its ground state, but that's >>>> exactly what one would expect. The other is the contribution from the >>>> penalty energy (E_constrain, it should be printed after each scf step), >>>> which is used to impose the constraint. >>>> An important thing is that this energy term is not physical and becomes >>>> negligible once your system reaches the target state.Therefore one should >>>> monitor this constraint energy, together with the constrained quantity, and >>>> make sure it goes to zero at some point. >>>> >>>> Once lambda is large enough and you reached the targeted state, >>>> E_constrain should be negligible w.r.t. the total energy and of the same >>>> order of the estimated scf accuracy. From that point on, the energy should >>>> not change if you further increase lambda, because your system fulfills >>>> (almost) exactly the constraint, so that E_constrain should stay to a very >>>> low value. >>>> >>>> HTH >>>> >>>> >>>> GS >>>> >>> >> >> _______________________________________________ >> Pw_forum mailing list >> Pw_forum at pwscf.org >> http://pwscf.org/mailman/listinfo/pw_forum >> > > > _______________________________________________ > Pw_forum mailing list > Pw_forum at pwscf.org > http://pwscf.org/mailman/listinfo/pw_forum > -------------- next part -------------- An HTML attachment was scrubbed... URL: http://pwscf.org/pipermail/pw_forum/attachments/20140310/6d3f589b/attachment.html
