<div dir="ltr"><div>Dear Cyrille,<br></div><br><div class="gmail_quote"><div dir="ltr" class="gmail_attr">Il giorno lun 18 gen 2021 alle ore 11:42 BARRETEAU Cyrille <<a href="mailto:cyrille.barreteau@cea.fr">cyrille.barreteau@cea.fr</a>> ha scritto:<br></div><blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex">
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<div>Dear Matteo,<br>
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<div>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..).</div>
<div>This is even more difficult in finite systems such as clusters or molecules where you can often have multiple magnetic states.<br></div></div></div></blockquote><div><br></div><div>Yes, in fact this is also my case: many magnetic states.<br></div><div> </div><blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex"><div><div style="direction:ltr;font-family:Times New Roman;color:rgb(0,0,0);font-size:10pt"><div>
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<div>Did you try to perform non-collinear calculations without SOC? Just to check that collinear configurations converge and are independent of the magnetization angle?</div></div></div></blockquote><div><br></div><div>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?</div><div><br></div><div>Thanks,</div><div><br></div><div>Matteo<br></div><div> </div><div><br></div><blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex"><div><div style="direction:ltr;font-family:Times New Roman;color:rgb(0,0,0);font-size:10pt">
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<div>Cyrille<br>
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<div style="font-family:Tahoma;font-size:13px"><b>Cyrille Barreteau</b><br>
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<div style="font-family:Tahoma;font-size:13px"><font size="2"><font face="Times New Roman">CEA Saclay<span style="background-color:white"></span></font><font face="Times New Roman">,
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</span></font>91191 Gif sur Yvette Cedex<span style="background-color:white"></span>, FRANCE
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6 47 53 66 52 (mobile) </font></font></font> </font></font></font><br>
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<div id="gmail-m_-5473609859592236609divRpF556433" style="direction:ltr"><font size="2" face="Tahoma" color="#000000"><b>De :</b> users [<a href="mailto:users-bounces@lists.quantum-espresso.org" target="_blank">users-bounces@lists.quantum-espresso.org</a>] de la part de Matteo Cococcioni [<a href="mailto:matteo.cococcioni@unipv.it" target="_blank">matteo.cococcioni@unipv.it</a>]<br>
<b>Envoyé :</b> lundi 18 janvier 2021 11:05<br>
<b>À :</b> Quantum ESPRESSO users Forum<br>
<b>Objet :</b> Re: [QE-users] constrained magnetization with non-colin and spin-orbit<br>
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<div>Dear Cyrille,</div>
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<div>thanks for your reply and advice.<br>
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<div dir="ltr" class="gmail_attr">Il giorno lun 18 gen 2021 alle ore 10:25 BARRETEAU Cyrille <<a href="mailto:cyrille.barreteau@cea.fr" rel="noopener noreferrer" target="_blank">cyrille.barreteau@cea.fr</a>> ha scritto:<br>
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<div>Dear Matteo</div>
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<div>If I understand well you want to calculate the magnetic anisotropy of a magnetic molecule.</div>
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<div>Yes, that's correct<br>
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<div>I am not sure I have understood well the way you proceed when you say that you "start" from a collinear lsda.</div>
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<div>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.<br>
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<div>I would say that you can try two strategies:</div>
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<div>i) using the force theorem as implemented in QE (one scf lsda calculation and then nscf with SOC starting from different theta angles..)</div>
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<div>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).
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<div>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)</div>
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<div>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.</div>
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<div>thanks again.</div>
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<div>Best regards,</div>
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<div>Matteo</div>
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<div>best</div>
<div>Cyrille</div>
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<div style="font-family:Tahoma;font-size:13px"><b>Cyrille Barreteau</b><br>
<div style="font-family:Tahoma;font-size:13px">
<div style="font-family:Tahoma;font-size:13px"><font size="2"><font face="Times New Roman">CEA Saclay<span style="background-color:white"></span></font><font face="Times New Roman">,
</font><font face="Times New Roman"><font face="Times New Roman"><font face="Times New Roman">IRAMIS,</font> SPEC</font></font><font face="Times New Roman"><font face="Times New Roman"><span style="background-color:white"> Bat. 771<br>
</span></font>91191 Gif sur Yvette Cedex<span style="background-color:white"></span>, FRANCE
</font><br>
<font face="Times New Roman"><font face="Times New Roman">~~~~~~~~~~~~~~~~~~~~~~~~~~~~</font><br>
</font><font face="Times New Roman"><font face="Times New Roman"><font face="Times New Roman">+33 1 69 08 38 56 /</font></font></font><font face="Times New Roman"><font face="Times New Roman"><font face="Times New Roman"><font face="Times New Roman"><font face="Times New Roman">+33
6 47 53 66 52 (mobile) </font></font></font> </font></font></font><br>
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de la part de Matteo Cococcioni [<a href="mailto:matteo.cococcioni@unipv.it" rel="noopener noreferrer" target="_blank">matteo.cococcioni@unipv.it</a>]<br>
<b>Envoyé :</b> dimanche 17 janvier 2021 11:09<br>
<b>À :</b> Quantum ESPRESSO users Forum<br>
<b>Objet :</b> [QE-users] constrained magnetization with non-colin and spin-orbit<br>
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<div>Dear all,</div>
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<div>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):</div>
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<div> noncolin = .true.<br>
lspinorb=.true.<br>
angle1(1) = 30.0<br>
angle1(2) = 30.0<br>
constrained_magnetization = 'atomic direction'</div>
<div> lambda = 1.0</div>
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<div>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.</div>
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<div>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. <br>
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<div>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).
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<div>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.</div>
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<div>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.</div>
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<div>Best regards,<br>
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<div>Matteo<br>
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<div>Matteo Cococcioni<br>
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<div>Department of Physics<br>
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University of Pavia<br>
Via Bassi 6, I-27100 Pavia, Italy<br>
tel +39-0382-987485<br>
<div>e-mail <a href="mailto:lucio.andreani@unipv.it" rel="noopener noreferrer" target="_blank">
matteo.cococcioni@unipv.it</a></div>
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<div>Matteo Cococcioni<br>
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<div>Department of Physics<br>
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University of Pavia<br>
Via Bassi 6, I-27100 Pavia, Italy<br>
tel +39-0382-987485<br>
<div>e-mail <a href="mailto:lucio.andreani@unipv.it" rel="noopener noreferrer" target="_blank">
matteo.cococcioni@unipv.it</a></div>
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_______________________________________________<br>
Quantum ESPRESSO is supported by MaX (<a href="http://www.max-centre.eu" rel="noreferrer" target="_blank">www.max-centre.eu</a>)<br>
users mailing list <a href="mailto:users@lists.quantum-espresso.org" target="_blank">users@lists.quantum-espresso.org</a><br>
<a href="https://lists.quantum-espresso.org/mailman/listinfo/users" rel="noreferrer" target="_blank">https://lists.quantum-espresso.org/mailman/listinfo/users</a></blockquote></div><br clear="all"><br>-- <br><div dir="ltr" class="gmail_signature"><div dir="ltr"><div><div dir="ltr"><div><div dir="ltr"><div>Matteo Cococcioni<br></div><div>Department of Physics<br></div>University of Pavia<br>Via Bassi 6, I-27100 Pavia, Italy<br>tel +39-0382-987485<br><div>e-mail <a href="mailto:lucio.andreani@unipv.it" target="_blank">matteo.cococcioni@unipv.it</a></div></div></div></div></div></div></div></div>