Dear Profs. Blaha and Marks,<div><br></div><div>Thanks for your answer, I really appreciated it: taught me a few differences between LAPW and pseudopotential calculations. The calculation actually converged after a few more iterations. It looks like the first inclusion of U is the most problematic - I started from U=1 eV and increased it to 4 eV in steps of 1 eV, and the subsequent runs took quite fewer steps to converge.</div>
<div><br></div><div>Thanks very much,</div><div><br></div><div>Marcos</div><div>Universidad de Cantabria, Spain</div><div><br><div class="gmail_quote">On Mon, Apr 25, 2011 at 9:34 PM, Laurence Marks <span dir="ltr"><<a href="mailto:L-marks@northwestern.edu">L-marks@northwestern.edu</a>></span> wrote:<br>
<blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex;">As Peter said, do NOT simply reduce the greed, it does not work the<br>
same as it does in PP calculations.<br>
<br>
More to the point, you/we need more information to know what is going<br>
on. Assuming that you are using the latest version (or similar) then<br>
<br>
grep -e :DIR -e GREED -e :FRMS -e :ENE -e :CHARG -e PRATT -e :DIS -e<br>
"MIXING SC" -e PLANE *.scf | tail -40<br>
<br>
will give more information and what is really going on...<br>
<div><div></div><div class="h5"><br>
On Mon, Apr 25, 2011 at 2:21 PM, Peter Blaha<br>
<<a href="mailto:pblaha@theochem.tuwien.ac.at">pblaha@theochem.tuwien.ac.at</a>> wrote:<br>
> The convergence behaviour is not very good, but it is not too bad either.<br>
><br>
> Check also :MMT or some :MMI0xx<br>
><br>
> For more complicated cases (metallic ??) it is well possible that one needs<br>
> more<br>
> than 40 iterations. Thus my suggestion is to keep going and submit another<br>
> job.<br>
><br>
> Sometimes it is better to keep the history (use -NI switch), sometimes it<br>
> can also<br>
> be better to remove the history (rm *.broy*; which will be done<br>
> automatically when<br>
> -NI is not supplied).<br>
><br>
> The mixing parameter has little importance with MSEC1, but still, a too<br>
> small mixing<br>
> can lead to too small steps and thus "pseudoconvergence" (this simply means,<br>
> that so<br>
> little new density is mixed, that eg. the total energy is not changing and<br>
> one thinks<br>
> the calculation is converged).<br>
><br>
> PRATT is most likely "useless" for your problem.<br>
><br>
> In LDA+U calculations it is easily possible to reach different states<br>
> (different<br>
> orbital occupations), which are stable and local minima. Once you have<br>
> reached<br>
> convergence, there is never a guarantee that this is the groundstate and<br>
> really<br>
> has the lowest energy.<br>
> The suggested procedure in the UG is NOT ALWAYS leading to the lowest state,<br>
> but often it will do.<br>
><br>
><br>
>> I have searched the list but I'm a bit confused with the posts, so I'll<br>
>> pose my questions here.<br>
>><br>
>> I am running LDA+U with and without spin-orbit coupling for a structure in<br>
>> a cell with the following cell parameters (Bohr):<br>
>><br>
>> P LATTICE,NONEQUIV.ATOMS: 14127_P4/mbm<br>
>> MODE OF CALC=RELA<br>
>> 10.353171 10.353171 43.972470 90.000000 90.000000 90.000000<br>
>><br>
>> and a cell sampling of 12x12x3, which gives 432 points in the BZ, 42 in<br>
>> the IBZ. My RKMAX is 8 - it was necessary to go to such high values to<br>
>> converge the spin moment of<br>
>> the system, as well as the energy down to 1 mRy. I followed the procedure<br>
>> stated in the manual: started with the LSDA calculation, then included<br>
>> spin-orbit coupling and now<br>
>> I am including the U gradually (well, at this point, just trying to...). I<br>
>> have to get to U=4 eV, so I'm growing it in steps of 1 eV.<br>
>><br>
>> Convergence was very good for the LSDA+U calculations without SOC, and<br>
>> they have finished, already (that is, I have already gotten to the 4 eV in<br>
>> U). However, I am having<br>
>> problems converging the scf, with the charge and energy distances (as<br>
>> obtained by grep convergence case.dayfile) oscillating, and never attaining<br>
>> convergence, which I set<br>
>> to ec=0.00001 and cc=0.0001 (the numbers are appended by the end of this<br>
>> message). More than 40 SCF steps have passed.<br>
>><br>
>> Usually, in pseudopotential calculations, one possible solution is to<br>
>> decrease the mixing weight of the charge densities for the following SCF<br>
>> step, and the other is to<br>
>> increase the smearing temperature. I would like to tweak with the mixing<br>
>> rather than increasing the temperature, if possible, because from my<br>
>> experience, increasing the<br>
>> temperature can sometimes lead to a non-magnetic state. However, I see<br>
>> from the mailing list that (at least in LAPW calculations), too small a<br>
>> mixing can lead to<br>
>> pseudo-convergence - which I don't understand what is. So, my questions<br>
>> are the following:<br>
>><br>
>> 1) What is the best thing to do to make my calculation converge: increase<br>
>> the mixing, or to diminish it? Should I change the mixing for MSEC1, and if<br>
>> so, by which amount?<br>
>> Or, would it be good to change to PRATT, instead? I am quite lost with<br>
>> regards to that.<br>
>> 2) Would the application of SOC to the already converged LSDA+U<br>
>> calculation yield too different results from starting from a converged<br>
>> LSDA+SOC with later inclusion of U?<br>
>> 3) What is the pseudo-convergence mentioned in previous emails in the<br>
>> list?<br>
>><br>
>> Of course, I will gladly provide more information, if needed.<br>
>><br>
>> Best regards,<br>
>><br>
>> Marcos<br>
>> Universidad de Cantabria, Spain<br>
>><br>
>> =======================================<br>
>><br>
>> Convergence of energy and charge distances:<br>
>><br>
>> :ENERGY convergence: 0 0.00001 .0002941150000000<br>
>> :CHARGE convergence: 0 0.0001 .0088826<br>
>> :ENERGY convergence: 0 0.00001 .0000916950000000<br>
>> :CHARGE convergence: 0 0.0001 .0085946<br>
>> :ENERGY convergence: 0 0.00001 .0000428400000000<br>
>> :CHARGE convergence: 0 0.0001 .0112915<br>
>> :ENERGY convergence: 0 0.00001 .0001772500000000<br>
>> :CHARGE convergence: 0 0.0001 .0113780<br>
>> :ENERGY convergence: 0 0.00001 .0002456850000000<br>
>> :CHARGE convergence: 0 0.0001 .0104415<br>
>> :ENERGY convergence: 0 0.00001 .0001420300000000<br>
>> :CHARGE convergence: 0 0.0001 .0083852<br>
>> :ENERGY convergence: 0 0.00001 .0000500150000000<br>
>> :CHARGE convergence: 0 0.0001 .0084675<br>
>> :ENERGY convergence: 0 0.00001 .0001809700000000<br>
>> :CHARGE convergence: 0 0.0001 .0134776<br>
>> :ENERGY convergence: 0 0.00001 .0001993400000000<br>
>> :CHARGE convergence: 0 0.0001 .0112308<br>
>> :ENERGY convergence: 0 0.00001 .0002392700000000<br>
>> :CHARGE convergence: 0 0.0001 .0104208<br>
>> :ENERGY convergence: 0 0.00001 .0002088150000000<br>
>> :CHARGE convergence: 0 0.0001 .0069138<br>
>> :ENERGY convergence: 0 0.00001 .0001630050000000<br>
>> :CHARGE convergence: 0 0.0001 .0109876<br>
>> :ENERGY convergence: 0 0.00001 .0002176700000000<br>
>> :CHARGE convergence: 0 0.0001 .0012609<br>
>> :ENERGY convergence: 0 0.00001 .0001806300000000<br>
>> :CHARGE convergence: 0 0.0001 .0042825<br>
>> :ENERGY convergence: 0 0.00001 .0000720450000000<br>
>> :CHARGE convergence: 0 0.0001 .0045301<br>
>> :ENERGY convergence: 0 0.00001 .0000129050000000<br>
>> :CHARGE convergence: 0 0.0001 .0011304<br>
>> :ENERGY convergence: 0 0.00001 .0002283150000000<br>
>> :CHARGE convergence: 0 0.0001 .0047456<br>
>> :ENERGY convergence: 0 0.00001 .0003098100000000<br>
>> :CHARGE convergence: 0 0.0001 .0100820<br>
>> :ENERGY convergence: 0 0.00001 .0003708750000000<br>
>> :CHARGE convergence: 0 0.0001 .0087276<br>
>> :ENERGY convergence: 0 0.00001 .0000788950000000<br>
>> :CHARGE convergence: 0 0.0001 .0090876<br>
>> :ENERGY convergence: 0 0.00001 .0000849050000000<br>
>> :CHARGE convergence: 0 0.0001 .0093747<br>
>> :ENERGY convergence: 0 0.00001 .0000842350000000<br>
>> :CHARGE convergence: 0 0.0001 .0079561<br>
>> :ENERGY convergence: 0 0.00001 .0000553500000000<br>
>> :CHARGE convergence: 0 0.0001 .0122027<br>
>> :ENERGY convergence: 0 0.00001 .0000434050000000<br>
>> :CHARGE convergence: 0 0.0001 .0109352<br>
>> :ENERGY convergence: 0 0.00001 .0000227750000000<br>
>> :CHARGE convergence: 0 0.0001 .0122136<br>
>> :ENERGY convergence: 0 0.00001 .0000194300000000<br>
>> :CHARGE convergence: 0 0.0001 .0121261<br>
>> :ENERGY convergence: 0 0.00001 .0000292700000000<br>
>> :CHARGE convergence: 0 0.0001 .0131197<br>
>> :ENERGY convergence: 0 0.00001 .0000360650000000<br>
>> :CHARGE convergence: 0 0.0001 .0110031<br>
>> :ENERGY convergence: 0 0.00001 .0000300950000000<br>
>> :CHARGE convergence: 0 0.0001 .0115123<br>
>> :ENERGY convergence: 0 0.00001 .0000323600000000<br>
>> :CHARGE convergence: 0 0.0001 .0099887<br>
>> :ENERGY convergence: 0 0.00001 .0000147550000000<br>
>> :CHARGE convergence: 0 0.0001 .0110331<br>
>> :ENERGY convergence: 0 0.00001 .0001196200000000<br>
>> :CHARGE convergence: 0 0.0001 .0005253<br>
>><br>
>><br>
>><br>
>> _______________________________________________<br>
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><br>
> --<br>
> -----------------------------------------<br>
> Peter Blaha<br>
> Inst. Materials Chemistry, TU Vienna<br>
> Getreidemarkt 9, A-1060 Vienna, Austria<br>
> Tel: <a href="tel:%2B43-1-5880115671" value="+4315880115671">+43-1-5880115671</a><br>
> Fax: <a href="tel:%2B43-1-5880115698" value="+4315880115698">+43-1-5880115698</a><br>
> email: <a href="mailto:pblaha@theochem.tuwien.ac.at">pblaha@theochem.tuwien.ac.at</a><br>
> -----------------------------------------<br>
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><br>
<br>
<br>
<br>
</div></div>--<br>
Laurence Marks<br>
Department of Materials Science and Engineering<br>
MSE Rm 2036 Cook Hall<br>
2220 N Campus Drive<br>
Northwestern University<br>
Evanston, IL 60208, USA<br>
Tel: <a href="tel:%28847%29%20491-3996" value="+18474913996">(847) 491-3996</a> Fax: <a href="tel:%28847%29%20491-7820" value="+18474917820">(847) 491-7820</a><br>
email: L-marks at northwestern dot edu<br>
Web: <a href="http://www.numis.northwestern.edu" target="_blank">www.numis.northwestern.edu</a><br>
Chair, Commission on Electron Crystallography of IUCR<br>
<a href="http://www.numis.northwestern.edu/" target="_blank">www.numis.northwestern.edu/</a><br>
Research is to see what everybody else has seen, and to think what<br>
nobody else has thought<br>
Albert Szent-Gyorgi<br>
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</div></div></blockquote></div><br></div>