Dear Juanjo, Thank you for the advice. We did try a DFT+U calculation only on the neodymium atoms, but it was also with the default number of bands. We saw similar results in terms of total magnetization as the other calculations we ran without the +U correction.
Thanks, Michael Graduate Student in Nuclear Engineering Department of Mechanical and Aerospace Engineering The Ohio State University From: pw_forum-bounces at pwscf.org [mailto:[email protected]] On Behalf Of Juanjo Mel?ndez Sent: Monday, June 16, 2014 1:37 PM To: PWSCF Forum Subject: Re: [Pw_forum] Nd2Fe14B Magnetization Dear Michael I think that the problem is the presence of Nd in your lattice. As far as I know, f-electrons are not only tricky to handle within a DFT formalism, but they constitute the border of its validity. I would not expect a great degree of accuracy in your calculations for any PP you may use. Anyway, you could try with DFT+U with the proper correction for correlated f-electrons (and maybe d-electrons from Fe as well). Sometimes it is hard to converge, but it could help. Anyway, I would not expect any miracle. BTW. Do not waste your time trying to change ecutrho. You are using a norm-conserving pseudopotential, so that ecutrho is meaningless. Good luck Juanjo Juan J. Mel?ndez Associate Professor Department of Physics ? University of Extremadura Avda. de Elvas, s/n 06006 Badajoz (Spain) Phone: +34 924 28 96 55 Fax: +34 924 28 96 51 Email: melendez at unex.es Web: http://materiales.unex.es/miembros/personal/jj-melendez/Index.html From: Kurth, Michael R.<mailto:[email protected]> Sent: Monday, June 16, 2014 5:52 PM To: PWSCF Forum<mailto:pw_forum at pwscf.org> Subject: Re: [Pw_forum] Nd2Fe14B Magnetization Dear Dr. Rebaza, Thank you for the reply. We did increase ecutrho to approximately 6 times the ecutwfc value and did not see a notable difference in the calculation. As far as the value of ecutwfc=260, we arrived at this value after running calculations at ecutwfc=300 and not observing a 1 mRy/atom difference in the total energy. We also have tested PBE and PW pseudopotentials but have not observed a difference in the total magnetization value. Sincerely, Michael Kurth Graduate Student in Nuclear Engineering Department of Mechanical and Aerospace Engineering The Ohio State University From: pw_forum-bounces at pwscf.org [mailto:[email protected]] On Behalf Of Arles V. Gil Rebaza Sent: Monday, June 16, 2014 11:28 AM To: PWSCF Forum Subject: Re: [Pw_forum] Nd2Fe14B Magnetization Dear Michael, are you sure that "ecutwfc = 260.0" is a enough value for your system, may be you should increse, and you're using the default value of "ecutrho", try to converge with this tag.!!! Best PhD. Arles V. GIl Rebaza Instituto de F?sica La Plata La Plata - Argentina 2014-06-16 12:16 GMT-03:00 Kurth, Michael R. <kurth.17 at buckeyemail.osu.edu<mailto:kurth.17 at buckeyemail.osu.edu>>: Hello, I am trying to calculate the magnetization of NdFeB which is a ferromagnetic material and a metal. This calculation has been done before using different methods than plane waves and pseudopotentials. Moreover, the magnetization per formula unit has been experimentally measured. The previous calculations and experimental values agree and report a magnetization per formula unit of around 37 Bohr Magneton. The previous calculations used the Generalized Gradient Approximation for the exchange correlation functional. We first tried the calculation using the default number of bands and the input file is attached below: &control calculation='scf' restart_mode='from_scratch', wf_collect=.TRUE., prefix='NdFeB', pseudo_dir = '/usr/local/espresso/espresso-5.0.3/pseudo/', outdir = '/fs/lustre/osu7834/NdFeB/' / &system ibrav=0, nat=68, ntyp=3, nspin=2, starting_magnetization(1)=0.6, starting_magnetization(2)=0.6, starting_magnetization(3)=0.6, ecutwfc = 260.0 occupations='smearing', smearing='mv', degauss=0.002 / &electrons conv_thr=1.0e-6 mixing_beta=0.02 mixing_mode = 'local-TF' / CELL_PARAMETERS {angstrom} 8.8 0.0 0.0 0.0 12.19 0.0 0.0 0.0 8.8 ATOMIC_SPECIES Nd 144.24 Nd.pbe-mt_fhi.UPF Fe 55.845 Fe.pbe-mt_fhi.UPF B 10.811 B.pbe-mt_fhi.UPF ATOMIC_POSITIONS {angstrom} B 5.54400 0.00000 3.25600 B 3.25600 0.00000 5.54400 B 7.65600 6.09500 7.65600 B 1.14400 6.09500 1.14400 Fe 4.40000 0.00000 0.00000 Fe 4.40000 6.09500 0.00000 Fe 0.00000 6.09500 4.40000 Fe 0.00000 0.00000 4.40000 Fe 4.40000 1.37747 4.40000 Fe 0.00000 7.47247 0.00000 Fe 0.00000 4.71753 0.00000 Fe 4.40000 10.81253 4.40000 Fe 0.85360 2.49895 0.85360 Fe 7.94640 2.49895 7.94640 Fe 5.25360 8.59395 3.54640 Fe 3.54640 8.59395 5.25360 Fe 5.25360 3.59605 3.54640 Fe 3.54640 3.59605 5.25360 Fe 0.85360 9.69105 0.85360 Fe 7.94640 9.69105 7.94640 Fe 2.79840 3.01093 2.79840 Fe 6.00160 3.01093 6.00160 Fe 7.19840 9.10593 1.60160 Fe 1.60160 9.10593 7.19840 Fe 7.19840 3.08407 1.60160 Fe 1.60160 3.08407 7.19840 Fe 2.79840 9.17907 2.79840 Fe 6.00160 9.17907 6.00160 Fe 4.99840 1.56032 1.97120 Fe 3.80160 1.56032 6.82880 Fe 6.37120 7.65532 8.20160 Fe 2.42880 7.65532 0.59840 Fe 0.59840 4.53468 2.42880 Fe 8.20160 4.53468 6.37120 Fe 1.97120 10.62968 4.99840 Fe 6.82880 1.56032 3.80160 Fe 3.80160 10.62968 6.82880 Fe 4.99840 10.62968 1.97120 Fe 2.42880 4.53468 0.59840 Fe 6.37120 4.53468 8.20160 Fe 8.20160 7.65532 6.37120 Fe 0.59840 7.65532 2.42880 Fe 6.82880 10.62968 3.80160 Fe 1.97120 1.56032 4.99840 Fe 3.15920 2.14544 0.34320 Fe 5.64080 2.14544 8.45680 Fe 4.74320 8.24044 1.24080 Fe 4.05680 8.24044 7.55920 Fe 7.55920 3.94956 4.05680 Fe 1.24080 3.94956 4.74320 Fe 0.34320 10.04456 3.15920 Fe 8.45680 2.14544 5.64080 Fe 5.64080 10.04456 8.45680 Fe 3.15920 10.04456 0.34320 Fe 4.05680 3.94956 7.55920 Fe 4.74320 3.94956 1.24080 Fe 1.24080 8.24044 4.74320 Fe 7.55920 8.24044 4.05680 Fe 8.45680 10.04456 5.64080 Fe 0.34320 2.14544 3.15920 Nd 2.34080 0.00000 2.34080 Nd 6.45920 0.00000 6.45920 Nd 6.74080 6.09500 2.05920 Nd 2.05920 6.09500 6.74080 Nd 7.56800 0.00000 1.23200 Nd 1.23200 0.00000 7.56800 Nd 5.63200 6.09500 5.63200 Nd 3.16800 6.09500 3.16800 K_POINTS {automatic} 4 4 4 0 0 0 This input file was prepared after checking convergence with respect to the energy cutoff and the number of points and did converge after 2 restart runs. Unfortunately, we obtained a magnetization of 25 Bohr Magneton/f.u. (which is too small). Furthermore, and after checking for convergence with respect to the number of bands (by adding more bands) we found that we end up with a magnetization of 50 Bohr Magneton/f.u. (which is too big). I also think that the degauss value used for smearing is small enough and can't be the problem. Are there any recommendations for what other parameters I could examine to help me get the right answer? Your help is greatly appreciated! Sincerely, Michael Kurth Graduate Student in Nuclear Engineering Department of Mechanical and Aerospace Engineering The Ohio State University _______________________________________________ Pw_forum mailing list Pw_forum at pwscf.org<mailto:Pw_forum at pwscf.org> http://pwscf.org/mailman/listinfo/pw_forum -- ###---------> Arles V. <---------### ________________________________ No virus found in this message. 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