[Pw_forum] Nd2Fe14B Magnetization
Juanjo Meléndez
melendez at unex.es
Mon Jun 16 19:37:10 CEST 2014
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. Meléndez
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.
Sent: Monday, June 16, 2014 5:52 PM
To: PWSCF Forum
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:pw_forum-bounces at pwscf.org] 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 Física La Plata
La Plata - Argentina
2014-06-16 12:16 GMT-03:00 Kurth, Michael R. <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 0.00.0 12.19 0.00.0 0.0 8.8ATOMIC_SPECIESNd 144.24 Nd.pbe-mt_fhi.UPFFe 55.845 Fe.pbe-mt_fhi.UPF B 10.811 B.pbe-mt_fhi.UPF ATOMIC_POSITIONS {angstrom}B 5.54400 0.00000 3.25600B 3.25600 0.00000 5.54400B 7.65600 6.09500 7.65600B 1.14400 6.09500 1.14400Fe 4.40000 0.00000 0.00000Fe 4.40000 6.09500 0.00000Fe 0.00000 6.09500 4.40000Fe 0.00000 0.00000 4.40000Fe 4.40000 1.37747 4.40000Fe 0.00000 7.47247 0.00000Fe 0.00000 4.71753 0.00000Fe 4.40000 10.81253 4.40000Fe 0.85360 2.49895 0.85360Fe 7.94640 2.49895 7.94640Fe 5.25360 8.59395 3.54640Fe 3.54640 8.59395 5.25360Fe 5.25360 3.59605 3.54640Fe 3.54640 3.59605 5.25360Fe 0.85360 9.69105 0.85360Fe 7.94640 9.69105 7.94640Fe 2.79840 3.01093 2.79840Fe 6.00160 3.01093 6.00160Fe 7.19840 9.10593 1.60160Fe 1.60160 9.10593 7.19840Fe 7.19840 3.08407 1.60160Fe 1.60160 3.08407 7.19840Fe 2.79840 9.17907 2.79840Fe 6.00160 9.17907 6.00160Fe 4.99840 1.56032 1.97120Fe 3.80160 1.56032 6.82880Fe 6.37120 7.65532 8.20160Fe 2.42880 7.65532 0.59840Fe 0.59840 4.53468 2.42880Fe 8.20160 4.53468 6.37120Fe 1.97120 10.62968 4.99840Fe 6.82880 1.56032 3.80160Fe 3.80160 10.62968 6.82880Fe 4.99840 10.62968 1.97120Fe 2.42880 4.53468 0.59840Fe 6.37120 4.53468 8.20160Fe 8.20160 7.65532 6.37120Fe 0.59840 7.65532 2.42880Fe 6.82880 10.62968 3.80160Fe 1.97120 1.56032 4.99840Fe 3.15920 2.14544 0.34320Fe 5.64080 2.14544 8.45680Fe 4.74320 8.24044 1.24080Fe 4.05680 8.24044 7.55920Fe 7.55920 3.94956 4.05680Fe 1.24080 3.94956 4.74320Fe 0.34320 10.04456 3.15920Fe 8.45680 2.14544 5.64080Fe 5.64080 10.04456 8.45680Fe 3.15920 10.04456 0.34320Fe 4.05680 3.94956 7.55920Fe 4.74320 3.94956 1.24080Fe 1.24080 8.24044 4.74320Fe 7.55920 8.24044 4.05680Fe 8.45680 10.04456 5.64080Fe 0.34320 2.14544 3.15920Nd 2.34080 0.00000 2.34080Nd 6.45920 0.00000 6.45920Nd 6.74080 6.09500 2.05920Nd 2.05920 6.09500 6.74080Nd 7.56800 0.00000 1.23200Nd 1.23200 0.00000 7.56800Nd 5.63200 6.09500 5.63200Nd 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
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