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<p style="margin-top:0;margin-bottom:0"><span style="font-size: 11pt;">Dear Lorenzo,</span></p>
<p style="margin-top:0;margin-bottom:0"><span style="font-size: 11pt;"><br>
</span></p>
<p style="margin-top:0;margin-bottom:0"><span style="font-size: 11pt;">Thank you for your response, yes I got convergence without the field in about 23 iterations, but the estimated error was much better at the earlier iterations than with the field.</span></p>
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</span></p>
<p style="margin-top:0;margin-bottom:0"><span style="font-size: 11pt;">I take it from your response you believe the issue lies with the convergence? My k-point grid was defined so that the mesh was equally spaced in reciprocal space, however I understand the
system is highly inhomogeneous in the field direction so I will try something like 16x16x16.</span></p>
<p style="margin-top:0;margin-bottom:0"><span style="font-size: 11pt;"><br>
</span></p>
<p style="margin-top:0;margin-bottom:0"><span style="font-size: 11pt;">I understand what you say about edir, I believe also that the system runs more efficiently with the magnetisation along the z-axis. Do you think overall the code is more efficient with say
edir = 3, </span></p>
<p style="margin-top:0;margin-bottom:0"><span style="font-size: 11pt;"></p>
<div>nspin = 4, <span style="font-size: 11pt;">angle1(1) = 90, </span><span style="font-size: 11pt;">angle2(1) = 0? Provided that's the correct way to set magnetisation along the x-axis?</span></div>
<div><span style="font-size: 11pt;"><br>
</span></div>
<div><span style="font-size: 11pt;">Many thanks,</span></div>
<div><span style="font-size: 11pt;"><br>
</span></div>
<div><span style="font-size: 11pt;">Alex</span></div>
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<p></p>
<p style="margin-top:0;margin-bottom:0"><span style="font-size: 11pt;"><br>
</span></p>
<p style="margin-top:0;margin-bottom:0"><span style="font-size: 11pt;">Subject: Re: [QE-users] Difficulty with convergence using tefield</span><br>
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<div class="PlainText">Message-ID:<br>
<CAG+GtJcU1YPM9MY5bsn8_p6pdg21FLrLXu9ZWN0vr==jMvho6w@mail.gmail.com><br>
Content-Type: text/plain; charset="utf-8"<br>
<br>
edir=1 and 2 are extremely inefficient in parallel. Use edir=3, rotate your<br>
slab. Does it converge without field? Also, your choic is a of k-points<br>
looks the opposite of correct: you need many points along the field<br>
direction.<br>
<br>
-- <br>
Lorenzo Paulatto<br>
Written on a virtual keyboard with real fingers<br>
<br>
On Sat, 29 Sep 2018, 20:43 Alex.Durie, <alex.durie@open.ac.uk> wrote:<br>
<br>
> Dear experts,<br>
><br>
> I am attempting to perform an scf calculation on a semi-infinite slab of<br>
> ferromagnetic cobalt surrounded by a vacuum with an electric field applied<br>
> perpendicular to the magnetisation, out-of-plane.<br>
><br>
> I am struggling to get convergence in the scf cycle. I achieved<br>
> satisfactory results using the same geometry and k-points without the field.<br>
><br>
> I have attempted to run it with ecutwfc = 30, and ecutrho at its default<br>
> value. Now I am attempting ecutwfc = 46, ecutrho = 238 (as recommended in<br>
> the header of the pseudopotential file).<br>
><br>
> I find in both cases the total energy and Harris-Foulkes estimate are<br>
> usually negative, and the estimated scf accuracy is very large, for each<br>
> cycle.<br>
><br>
> The runtime for larger ecutwfc and ecutrho, is much longer.<br>
><br>
> Is there something I'm doing wrong, or do I need to alter my expectations<br>
> of runtime? Please see input file below.<br>
><br>
> I am running the code with MPI, on 4 cores. At 12 iterations, the CPU time<br>
> is 24737.9 secs, the total energy is -377.46347734 Ry, the Harris-Foulkes<br>
> estimate is -1293.19368730 Ry and the estimated scf accuracy is <<br>
> 3322.28583637 Ry. I have also noticed the "Adding external electric field"<br>
> block is duplicated on each cycle, though I suspect that's normal.<br>
><br>
> Many thanks<br>
><br>
> Alex Durie<br>
> PhD student<br>
> The Open University<br>
> United Kingdom<br>
><br>
> &control<br>
> calculation='scf'<br>
> restart_mode='from_scratch',<br>
> pseudo_dir = '/home/alex/QE/pslibrary.1.0.0/pz/PSEUDOPOTENTIALS/',<br>
> outdir='./'<br>
> prefix='co'<br>
> tefield = .true.<br>
> dipfield = .true.<br>
> /<br>
> &system<br>
> ibrav = 8,<br>
> celldm(1) =4.82388,<br>
> celldm(2) =8.,<br>
> celldm(3) =1.,<br>
> nat= 5,<br>
> ntyp= 1,<br>
> ecutwfc = 46.0<br>
> ecutrho = 238.0<br>
> nspin = 2<br>
> occupations='smearing', smearing='cold', degauss=0.02<br>
> starting_magnetization = -1<br>
> nbnd = 45<br>
> edir = 2<br>
> emaxpos = 0.41<br>
> eopreg = 0.59<br>
> eamp = 0.000243<br>
> /<br>
> &electrons<br>
> electron_maxstep = 500<br>
> diagonalization='cg'<br>
> conv_thr = 1.0e-6<br>
> mixing_beta = 0.3<br>
> /<br>
> ATOMIC_SPECIES<br>
> Co 58.933195 Co.pz-n-kjpaw_psl.1.0.0.UPF<br>
> ATOMIC_POSITIONS {bohr}<br>
> Co 0.0000000 0.0000000 0.000000<br>
> Co 2.4119400 3.4110000 2.411940<br>
> Co 0.0000000 6.8220000 0.000000<br>
> Co 2.4119400 10.2330000 2.411940<br>
> Co 0.0000000 13.6440000 0.000000<br>
> K_POINTS {automatic}<br>
> 16 2 16 0 0 0<br>
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