Dear Ben Liew,
If one is lucky, the system might converge to the right magnetic ground state with a "random guess". Yet if the system has several local minima, or the initial guess is very far from the true magnetic ordering, one might get very bad initial densities (total and spin density, or spin-up and spin-down densities), leading to difficulties in convergence and maybe even divergence. Yet-another-issue might be bad description of the electronic structure with the GGA's, I seem to remember that in the case of MnO2 the GGA gives reasonable results, even if the electronic band gap is naturally much too small (and using the smearing should help to get a convergence anyway).
I would myself start by trying a weakly ferromagnetic guess (for example 'starting_magnetization(1) = 0.2' and seeing if something happens. If it converges, or doesn't, I would then see if an anti-ferromagnetic solution might also make sense (two types of Mn atoms in cell, etc).
Greetings, apsi -=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=- Ari Paavo Seitsonen / ari.p.seitso...@iki.fi / http://www.iki.fi/~apsi/ Ecole Normale Supérieure (ENS), Département de Chimie, Paris Mobile (F) : +33 789 37 24 25 (CH) : +41 79 71 90 935 On Wed, 5 Aug 2015, ben liew wrote:
Dear Bahadir, Thanks for your comments. I will try using a lower mixing_beta and change the mixing_mode='local-TF'. Dear Ari Paavo Seitsonen, Thanks. I have no knowledge on the magnetism of my system. How could I know what value of starting_magnetization that I should use in my slab calculation? Does the starting_magnetization affect the convergence of my calculation? Thank you Best Regards, Ben Liew Ph.D Student Fuel Cell Institute, The National University of Malaysia, 43600 Bangi, Selangor, Malaysia. Contact no. : +6016 552 0878 Email : liewkien...@gmail.com On Wed, Aug 5, 2015 at 5:20 PM, Bahadır salmankurt <bsalmank...@gmail.com> wrote: Dear Ari P Seitsonen, I didnt know that mixing_mode='local-TF' effect initial magnetic moments. thanks for this. By the way, Do you know about e field configuration? for example, for slab + molecule systems whose atomic positions are in 0.5 and 0.65 along z direction , respectively, what must values of the emaxpos and eopreg be? Bests Bahadir 2015-08-05 10:59 GMT+03:00 Ari P Seitsonen <ari.p.seitso...@iki.fi>: Dear Ben Liew, Without looking at the structure itself, adding to the previous comment about the algorithm for mixing, you have not really given any initial magnetic moments even if you have 'nspin = 2': The 'starting_magnetization(1) = 0.0' does not give any preferential spin ordering. Do you know something about this, is the system expected to be ferromagnetic, antiferromagnetic, ...? Tiny issues, I usually do the first calculation without the surface dipole as it makes the convergence always a bit trickier; and your 'B ~= 2 * A', but you give the same number of k points in both directions. (I usually tend to use smearing schemes where the occupations are guaranteed to be in the physical range of [0:1], but this is just a personal preference and should thus be ignored) Greetings, apsi -=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=* =- Ari Paavo Seitsonen / ari.p.seitso...@iki.fi / http://www.iki.fi/~apsi/ Ecole Normale Supérieure (ENS), Département de Chimie, Paris Mobile (F) : +33 789 37 24 25 (CH) : +41 79 71 90 935 On Wed, 5 Aug 2015, ben liew wrote: Dear PWSCF users, Hi, I am a new user of Pwscf. I am working on slab calculation for pyrolusite MnO2 (110) surface with 3 atomic layers calculation and fixed bottom 2 layers and only top atomic layer is allowed to be relaxed. I have also include the dipole correction for the calculation to counteract with the interaction between slabs. However, my calculation doesn't seems to be converged as the scf accuracy is not decreasing over each iteration. Below is the estimated scf accuracy after hundreds of iterations, it is not converging estimated scf accuracy < 373.64728976 Ry estimated scf accuracy < 106.52177156 Ry estimated scf accuracy < 96.97567125 Ry estimated scf accuracy < 207.03807187 Ry estimated scf accuracy < 132.53045831 Ry estimated scf accuracy < 77.19101827 Ry estimated scf accuracy < 112.41885075 Ry estimated scf accuracy < 93.27430429 Ry estimated scf accuracy < 116.68049786 Ry estimated scf accuracy < 587.09711027 Ry estimated scf accuracy < 374.45312501 Ry estimated scf accuracy < 106.89811469 Ry estimated scf accuracy < 96.84898888 Ry estimated scf accuracy < 207.83006869 Ry estimated scf accuracy < 132.74588293 Ry estimated scf accuracy < 77.09445200 Ry estimated scf accuracy < 112.41688597 Ry estimated scf accuracy < 93.57796273 Ry estimated scf accuracy < 116.25663912 Ry estimated scf accuracy < 587.39968959 Ry estimated scf accuracy < 374.91438307 Ry estimated scf accuracy < 106.71641516 Ry estimated scf accuracy < 96.75392736 Ry I have include my input file as followed. Can anyone tell me is that any problem with my input file? &control calculation = 'relax' tstress=.true. tprnfor=.true. pseudo_dir='/home/ben/Downloads/espresso-5.1.2/pseudo' outdir='./vc3' prefix='pyrolusite' tefield=.true. dipfield=.true. / &system ibrav=8, A=2.8563, B=6.2199, C=20.0 nat=18, ntyp=2, starting_magnetization(1)=0.0 nspin=2 ecutwfc=37.0 ecutrho=250.0 occupations='smearing' smearing='m-v' degauss=0.01 edir=3 emaxpos=0.5 eopreg=0.1 eamp=0.001 / &electrons electron_maxstep=500 conv_thr=1.0d-6 mixing_beta=0.7 / &ions ion_dynamics='bfgs' / ATOMIC_SPECIES Mn 54.9380 Mn.pbe-spn-kjpaw_psl.0.3.1.UPF O 15.9994 O.pbe-kjpaw.UPF ATOMIC_POSITIONS (angstrom) O 1.428129 3.109734 0.000000 0 0 0 O 1.428129 0.000241 0.652526 0 0 0 Mn 1.428129 3.109896 1.883398 0 0 0 O 0.000000 1.885646 1.883398 0 0 0 O 0.000000 4.334118 1.883398 0 0 0 Mn 0.000000 0.000062 1.883398 0 0 0 O 0.000000 5.014614 4.987475 0 0 0 O 0.000000 1.205401 4.987475 0 0 0 Mn 0.000000 3.109816 4.987475 0 0 0 Mn 1.428129 0.000027 4.987475 0 0 0 O 1.428129 3.109734 3.767387 0 0 0 O 1.428129 0.000241 3.114269 0 0 0 O 1.428129 3.109734 6.207560 O 1.428129 0.000241 6.860698 Mn 1.428129 3.109896 8.091569 O 0.000000 1.885646 8.091569 O 0.000000 4.334118 8.091569 Mn 0.000000 0.000062 8.091569 K_POINTS (automatic) 5 5 1 0 0 0 Your comments and suggestion is much appreciated.Thank you. Best Regards, Ben Liew Ph.D Student Fuel Cell Institute, The National University of Malaysia, 43600 Bangi, Selangor, Malaysia. Contact no. : +6016 552 0878 Email : liewkien...@gmail.com _______________________________________________ Pw_forum mailing list Pw_forum@pwscf.org http://pwscf.org/mailman/listinfo/pw_forum _______________________________________________ Pw_forum mailing list Pw_forum@pwscf.org http://pwscf.org/mailman/listinfo/pw_forum
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