<div dir="ltr">It is in the second mail in this thread. Mr. Lorenzo Paulatto said the problem may be because the unit cell is too small.<br><div class="ebc gmail-vF"><div class="gmail-Iyc gmail-d-k-l"> </div></div></div><div class="gmail_extra"><br><div class="gmail_quote">On Wed, Dec 14, 2016 at 7:45 PM, Paolo Giannozzi <span dir="ltr"><<a href="mailto:p.giannozzi@gmail.com" target="_blank">p.giannozzi@gmail.com</a>></span> wrote:<br><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"><span class="">On Wed, Dec 14, 2016 at 3:00 PM, sayan chaudhuri <<a href="mailto:csayan895@gmail.com">csayan895@gmail.com</a>> wrote:<br>
<br>
> How to get rid of the small unit cell problem?<br>
<br>
</span>what is the "small unit cell problem"?<br>
<br>
Paolo<br>
<div><div class="h5">> When it is a pure system, Wycoff positions with Atomic positions card set<br>
> at alat works. So, is there any definite procedure to give the position of<br>
> the atoms in the system when I am doping in the system?<br>
><br>
> Thanking you,<br>
> Sayan Chaudhuri<br>
><br>
> On Fri, Dec 9, 2016 at 7:07 PM, Lorenzo Paulatto<br>
> <<a href="mailto:lorenzo.paulatto@impmc.upmc.fr">lorenzo.paulatto@impmc.upmc.<wbr>fr</a>> wrote:<br>
>><br>
>> It may be difficult to converge LDA+U calculations in general, starting<br>
>> with<br>
>> initial magnetizations that aren't absurd may help<br>
>><br>
>> hth<br>
>><br>
>> On Friday, December 9, 2016 5:29:01 PM CET Максим Арсентьев wrote:<br>
>> > Dear Lorenzo,<br>
>> ><br>
>> > I have the same problem - cannot achieve SCF convergence. I use higher<br>
>> > ecutwfc = 39.0, ecutrho = 300 but not coverging.<br>
>> ><br>
>> > Regards, Maxim Arsentev.<br>
>> ><br>
>> > 2016-12-09 12:52 GMT+04:00 Lorenzo Paulatto<br>
>> > <<a href="mailto:lorenzo.paulatto@impmc.upmc.fr">lorenzo.paulatto@impmc.upmc.<wbr>fr</a>><br>
>> > > Dear Sayan,<br>
>> > > it looks to me like your unit cell is too small, the atoms are all<br>
>> > > crumped<br>
>> > > together. Please note that celldm(1) is specified in bohr atomic<br>
>> > > units.<br>
>> > ><br>
>> > > Also:<br>
>> > > 1. a cutoff of 30Ry is probably very small for BHS pseudopotentials<br>
>> > > 2. ecutrho=default (4*ecutwfc ) is probably not enough for all the<br>
>> > > ultrasoft<br>
>> > > pseudopotentials you are using<br>
>> > ><br>
>> > > I would recommend you first spend some time reproducin the<br>
>> > > single-element<br>
>> > > metal, and once you can correctly reproduce geometry, band structure,<br>
>> > > physical<br>
>> > > properties, you move to simulating the alloy.<br>
>> > ><br>
>> > > HTH<br>
>> > ><br>
>> > > On Friday, December 9, 2016 1:59:44 PM CET sayan chaudhuri wrote:<br>
>> > > > Hi,<br>
>> > > ><br>
>> > > > I am running QE self - consistently for my heusler alloy(Fe2TiSn)<br>
>> > > ><br>
>> > > > system, where 25% of Sn were replaced by Sb. But after 800<br>
>> > > > iterations<br>
>> > > > and<br>
>> > > > almost 3 hours of running also still it is not converged.<br>
>> > > > The code I am using is added bellow. Please tell me what is the<br>
>> > > > source<br>
>> > > > of<br>
>> > > > error.<br>
>> > > ><br>
>> > > > Thanking you,<br>
>> > > ><br>
>> > > > Sayan Chaudhuri<br>
>> > > ><br>
>> > > > *&control prefix='fts', calculation = 'scf', verbosity =<br>
>> > > > 'low', pseudo_dir = '/home/ltp/Desktop/espresso-5.<wbr>4.0/pseudo',<br>
>> > > > outdir = './tmp', / &system ibrav=2 celldm(1)=11.43,<br>
>> > > > nat=16, ntyp=4, nspin=2, ecutwfc=30.0,<br>
>> > > > starting_magnetization(1) = 0.0, starting_magnetization(2) =<br>
>> > > > 0.0,<br>
>> > > > starting_magnetization(3) = 0.5, starting_magnetization(3) =<br>
>> > > > 0.0,<br>
>> > > > occupations='tetrahedra', / &electrons electron_maxstep =<br>
>> > > > 3000,<br>
>> > > > diagonalization = 'david', mixing_mode = 'plain', conv_thr =<br>
>> > > > 1e-8,<br>
>> > > > mixing_beta=0.1, /ATOMIC_SPECIES Sb 121.76 Sb.pz-bhs.UPF Sn<br>
>> > > > 118.71 Sn.pz-dn-rrkjus_psl.0.2.UPF Fe 55.845<br>
>> > > > Fe.pz-sp-van_ak.UPF<br>
>> > > > Ti 47.867 Ti.pz-sp-van.UPFATOMIC_<wbr>POSITIONS {crystal} Sb<br>
>> > > > 0.000000000 0.000000000 0.000000000 Sn<br>
>> > > > 0.000000000 0.500000000 0.500000000 Sn<br>
>> > > > 0.500000000 0.000000000 0.500000000 Sb<br>
>> > > > 0.500000000 0.500000000 0.000000000 Fe<br>
>> > > > 0.250000000 0.250000000 0.250000000 Fe<br>
>> > > > 0.750000000 0.750000000 0.750000000 Fe<br>
>> > > > 0.750000000 0.750000000 0.250000000 Fe<br>
>> > > > 0.250000000 0.250000000 0.750000000 Fe<br>
>> > > > 0.750000000 0.250000000 0.750000000 Fe<br>
>> > > > 0.250000000 0.750000000 0.250000000 Fe<br>
>> > > > 0.250000000 0.750000000 0.750000000 Fe<br>
>> > > > 0.750000000 0.250000000 0.250000000 Ti<br>
>> > > > 0.500000000 0.500000000 0.500000000 Ti<br>
>> > > > 0.500000000 0.000000000 0.000000000 Ti<br>
>> > > > 0.000000000 0.500000000 0.000000000 Ti<br>
>> > > > 0.000000000 0.000000000 0.500000000 K_POINTS<br>
>> > > > {automatic}<br>
>> > > > 2 2 2 0 0 0*<br>
>> > ><br>
>> > > --<br>
>> > > Dr. Lorenzo Paulatto<br>
>> > > IdR @ IMPMC -- CNRS & Université Paris 6<br>
>> > > phone: +33 (0)1 44275 084 / skype: paulatz<br>
>> > > www: <a href="http://www-int.impmc.upmc.fr/~paulatto/" rel="noreferrer" target="_blank">http://www-int.impmc.upmc.fr/~<wbr>paulatto/</a><br>
>> > > mail: 23-24/4é16 Boîte courrier 115, 4 place Jussieu 75252 Paris<br>
>> > > Cédex 05<br>
>> > ><br>
>> > > ______________________________<wbr>_________________<br>
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>><br>
>><br>
>> --<br>
>> Dr. Lorenzo Paulatto<br>
>> IdR @ IMPMC -- CNRS & Université Paris 6<br>
>> phone: +33 (0)1 44275 084 / skype: paulatz<br>
>> www: <a href="http://www-int.impmc.upmc.fr/~paulatto/" rel="noreferrer" target="_blank">http://www-int.impmc.upmc.fr/~<wbr>paulatto/</a><br>
>> mail: 23-24/4é16 Boîte courrier 115, 4 place Jussieu 75252 Paris Cédex 05<br>
>><br>
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<br>
<br>
--<br>
</div></div>Paolo Giannozzi, Dip. Scienze Matematiche Informatiche e Fisiche,<br>
Univ. Udine, via delle Scienze 208, 33100 Udine, Italy<br>
Phone +39-0432-558216, fax +39-0432-558222<br>
<div class="HOEnZb"><div class="h5"><br>
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