<html><head></head><body style="word-wrap: break-word; -webkit-nbsp-mode: space; -webkit-line-break: after-white-space; "><br><div><div>Il giorno 13/ago/2010, alle ore 01.23, Alejandro Rébola ha scritto:</div><br class="Apple-interchange-newline"><blockquote type="cite"><div>Dear all,<br><br>I'm performing a scf calculation for an AFM structure. I fix the magnetic<br>moments of the Fe ions using, for instance:<br><br>starting_magnetization(1)=0.7<br>starting_magnetization(2)=-0.7<br><br>constrained_magnetization='atomic'<br><br>I use the experimental structure of the system and perform a scf<br>calculation for different magnetic moments (I want to estimate the GS<br>magnetic moment).<br><br>My problem is that the system only converges for one value of the starting<br>magnetization (0.5) and doesn't converge in all the other cases I've<br>tried.<br>According to the pwscf documentation, LAMBDA, the Lagrange multiplier for<br>the magnetic penalty term, ".. is reduced in the first iterations and is<br>increased slowly up to the input value." (I've tried LAMBDA=1,10,20,30,50)<br></div></blockquote><div><br></div>Which version of the code are you using? In v4.2 the documentation about lambda reads:<br><div><br></div><div><div> Variable: lambda</div><div> </div><div> Type: REAL</div><div> See: constrained_magnetization</div><div> Default: 1.d0</div><div> Description: parameter used for constrained_magnetization calculations</div><div> N.B.: if the scf calculation does not converge, try to reduce lambda</div><div> to obtain convergence, then restart the run with a larger lambda</div><div><br></div><div>which I think is consistent with what the code does (i.e., lambda in NOT reduced and then increased automatically).</div><div>Please try what suggested in the Nota Bene. You may also need to play a little bit with the mixing_beta value. </div><div><br></div><div>The constraints on the magnetic moments are applied to the system in subroutine PW/add_bfield.f90.</div></div><br><blockquote type="cite"><div>Then, could it be that I should use much bigger values for LAMBDA? Is<br>there a default value for it? I couldn't find it.<br></div></blockquote><div><br></div><div>The default is 1.d0, as stated in the documentation.</div><div><br></div>HTH</div><div><br></div><div>GS</div><div><br><blockquote type="cite"><div><br>Thank you in advance for you help.<br><br>Best regards,<br><br>Alejandro<br><br>_______________________________________________<br>Pw_forum mailing list<br><a href="mailto:Pw_forum@pwscf.org">Pw_forum@pwscf.org</a><br>http://www.democritos.it/mailman/listinfo/pw_forum<br></div></blockquote></div><br><div>
<div><span class="Apple-style-span" style="color: rgb(126, 126, 126); font-size: 16px; font-style: italic; "><br class="Apple-interchange-newline">§ Gabriele Sclauzero, EPFL SB ITP CSEA</span></div><div><font class="Apple-style-span" color="#7E7E7E"><i> PH H2 462, Station 3, CH-1015 Lausanne</i></font></div>
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