Dear Cyrille, Il giorno lun 18 gen 2021 alle ore 11:42 BARRETEAU Cyrille < [email protected]> ha scritto:
> Dear Matteo, > Non collinear calculations are usually very difficult to converge with QE > (usually codes based on localized basis set are easier to converge since I > guess there are less degrees of freedom..). > This is even more difficult in finite systems such as clusters or > molecules where you can often have multiple magnetic states. > Yes, in fact this is also my case: many magnetic states. > Did you try to perform non-collinear calculations without SOC? Just to > check that collinear configurations converge and are independent of the > magnetization angle? > I only got convergence with SOC. without SOC I haven't tried yet but I will. I have to go back to the scalar-relativistic PP for that, right? Thanks, Matteo > Cyrille > > ======================== > *Cyrille Barreteau* > CEA Saclay, IRAMIS, SPEC Bat. 771 > 91191 Gif sur Yvette Cedex, FRANCE > ~~~~~~~~~~~~~~~~~~~~~~~~~~~~ > +33 1 69 08 38 56 /+33 6 47 53 66 52 (mobile) > email: [email protected] > Web: http://iramis.cea.fr/Pisp/cyrille.barreteau/ > ======================== > ------------------------------ > *De :* users [[email protected]] de la part de > Matteo Cococcioni [[email protected]] > *Envoyé :* lundi 18 janvier 2021 11:05 > *À :* Quantum ESPRESSO users Forum > *Objet :* Re: [QE-users] constrained magnetization with non-colin and > spin-orbit > > Dear Cyrille, > > thanks for your reply and advice. > > Il giorno lun 18 gen 2021 alle ore 10:25 BARRETEAU Cyrille < > [email protected]> ha scritto: > >> Dear Matteo >> >> If I understand well you want to calculate the magnetic anisotropy of a >> magnetic molecule. >> > > Yes, that's correct > > >> I am not sure I have understood well the way you proceed when you say >> that you "start" from a collinear lsda. >> >> > Well, I tried to start a non collinear calculation of this system from > scratch, but I could never achieve convergence. The convergence with lsda > is much more robust and using tot_magnetization I could achieve both a > ferromagnetic and an antiferromagnetic ground state. Then I tried to use > the charge-density of these ground states to initialize the non-collinear > calculation (of course after updating the Mo PP to its fully relativistic > version) with spin-orbit. This way I manage to converge to the same AFM and > FM ground state with the non-collinear calculation. Now I want to use these > calculations as starting points to take the magnetic moments away from the > z direction to which they are (anti)aligned. > > >> I would say that you can try two strategies: >> >> i) using the force theorem as implemented in QE (one scf lsda calculation >> and then nscf with SOC starting from different theta angles..) >> > > ok, I hadn't thought of this. Maybe it's sufficient to estimate the MAE. > If you initialize just the theta angle (angle1) will the modulus of the > magnetic moment be preserved with respect to the lsda or collinear ground > state it starts from? How does the code choose the angle phi (angle2) in > this case? In presence of SOC this also might make a difference and > contribute to the MAE (unless the system has a cylindrical symmetry around > the easy axis, which is not my case). > > >> ii) use the magnetic constraint with penalization parameter lambda and >> perform a scf calculation. It will be more delicate but maybe more precise >> (not sure since you might face convergence problems) >> >> > This is what I was trying to do (see above, also): I am trying to change > angle1 with lambda. I wanted to do a scf calculation to leave the system > free to chose angle2. But the convergence is very delicate. Actually there > seems to be no finite contribution to the potential from the constraint, so > the calculation goes on for a while without changing the angles from their > starting value and then suddenly crashes (not sure why). It seems that the > variable pointlist is never different from 0 in my case which causes the > potential to be insensitive to lambda. But I haven't yet understood why. > > thanks again. > > Best regards, > > Matteo > > > >> best >> Cyrille >> >> >> >> ======================== >> *Cyrille Barreteau* >> CEA Saclay, IRAMIS, SPEC Bat. 771 >> 91191 Gif sur Yvette Cedex, FRANCE >> ~~~~~~~~~~~~~~~~~~~~~~~~~~~~ >> +33 1 69 08 38 56 /+33 6 47 53 66 52 (mobile) >> email: [email protected] >> Web: http://iramis.cea.fr/Pisp/cyrille.barreteau/ >> ======================== >> ------------------------------ >> *De :* users [[email protected]] de la part de >> Matteo Cococcioni [[email protected]] >> *Envoyé :* dimanche 17 janvier 2021 11:09 >> *À :* Quantum ESPRESSO users Forum >> *Objet :* [QE-users] constrained magnetization with non-colin and >> spin-orbit >> >> >> Dear all, >> >> I am trying to run some calculations on a molecule with two magnetic ions >> (Mo) and I want to use the non collinear spin with spin-orbit to calculate >> the energy needed to change their direction. Starting from a collinear >> (lsda) calculation I managed to converge the non-collinear one in a >> ferromagnetic configuration, with magnetic moments aligned along z. Now I >> am using this ground state as starting point for a calculation where one or >> both spins are somehow deviated from the z direction. Following the >> instructions in INPUT_PW I am using the following settings (in &system): >> >> noncolin = .true. >> lspinorb=.true. >> angle1(1) = 30.0 >> angle1(2) = 30.0 >> constrained_magnetization = 'atomic direction' >> lambda = 1.0 >> >> where species 1 and 2 correspond to the two Mo, angle1 is the angle I >> want to have between z and the final magnetization, lambda is the strength >> of the quadratic constraint. >> >> If I start from the potential of the ground state with the magnetization >> along z, the code starts with no problem and even pretends to converge for >> a number of iterations. Then suddenly the energy explodes and the code >> crashes saying that there are too many not converged eigenvalues. >> While it seems converging nothing relevant seems to happen to angles: the >> constraint energy remains almost the same and the magnetization of both >> atoms maintains its original direction (aside small fluctuations). The same >> behavior is observed independently from the value of lambda (which is very >> strange) and beta (the mixing parameter). >> >> looking into the code (add_bfield.f90) the implementation of the >> constraint seems fine, as far as I can tell (except that the code tries to >> constraint all magnetic moments once a lambda is present, which I fixed), >> and the potential seems to get a term from the constraint on magnetization. >> So I would expect it to do something. >> >> Does anyone have any experience with this type of calculations? What am I >> missing or not doing right? Thanks in advance for any help/advice. >> >> Best regards, >> >> Matteo >> >> -- >> Matteo Cococcioni >> Department of Physics >> University of Pavia >> Via Bassi 6, I-27100 Pavia, Italy >> tel +39-0382-987485 >> e-mail [email protected] <[email protected]> >> _______________________________________________ >> Quantum ESPRESSO is supported by MaX (www.max-centre.eu) >> users mailing list [email protected] >> https://lists.quantum-espresso.org/mailman/listinfo/users > > > > -- > Matteo Cococcioni > Department of Physics > University of Pavia > Via Bassi 6, I-27100 Pavia, Italy > tel +39-0382-987485 > e-mail [email protected] <[email protected]> > _______________________________________________ > Quantum ESPRESSO is supported by MaX (www.max-centre.eu) > users mailing list [email protected] > https://lists.quantum-espresso.org/mailman/listinfo/users -- Matteo Cococcioni Department of Physics University of Pavia Via Bassi 6, I-27100 Pavia, Italy tel +39-0382-987485 e-mail [email protected] <[email protected]>
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