Hi Yun-Peng If your objective is really to determine quantitatively the value of the magnetic anisotropy I think that it is an impossible task to get a precision of 0.01meV!!!
Already below 0.1meV it is quite delicate but 0.01meV is just hopeless! Good luck Cyrille ======================== Cyrille Barreteau CEA Saclay, IRAMIS, SPEC Bat. 771 91191 Gif sur Yvette Cedex, FRANCE ~~~~~~~~~~~~~~~~~~~~~~~~~~~~ DTU Nanotech Ørsteds Plads, building 345E DK-2800 Kgs. Lyngby, DENMARK ~~~~~~~~~~~~~~~~~~~~~~~~~~~~ +33 1 69 08 29 51 /+33 6 47 53 66 52 (mobile) (Fr) +45 45 25 63 12/ +45 28 72 55 18 (mobile) (Dk) email: [email protected] /[email protected] Web: http://iramis.cea.fr/Pisp/cyrille.barreteau/ ======================== ________________________________ De : [email protected] [[email protected]] de la part de peter [[email protected]] Envoyé : samedi 12 septembre 2015 23:33 À : [email protected] Objet : Re: [Pw_forum] magnetic anisotropy calculation using fully-relativistic PPs Hi Cyrille, Since magnetic anisotropy energy is very small (~0.01 meV per atom in my system), do I need to use higher cutoff energies to account for such small energy scale? best, Yun-Peng On 09/12/2015 03:30 PM, BARRETEAU Cyrille wrote: Dear Yun-Peng, >From experience I can just say that calculation using fully-relativistic PP >can be really difficult to converge and sometimes almost impossible to achieve >the desired accuracy (especially since magneto-crystalline anisotropy requires >very strict convergence thresholds). You can play with broadening and k points >sampling. Cyrille ======================== Cyrille Barreteau CEA Saclay, IRAMIS, SPEC Bat. 771 91191 Gif sur Yvette Cedex, FRANCE ~~~~~~~~~~~~~~~~~~~~~~~~~~~~ DTU Nanotech Ørsteds Plads, building 345E DK-2800 Kgs. Lyngby, DENMARK ~~~~~~~~~~~~~~~~~~~~~~~~~~~~ +33 1 69 08 29 51 /+33 6 47 53 66 52 (mobile) (Fr) +45 45 25 63 12/ +45 28 72 55 18 (mobile) (Dk) email: [email protected]<mailto:[email protected]> /[email protected]<mailto:[email protected]> Web: <http://iramis.cea.fr/Pisp/cyrille.barreteau/> http://iramis.cea.fr/Pisp/cyrille.barreteau/ ======================== ________________________________ De : [email protected]<mailto:[email protected]> [[email protected]<mailto:[email protected]>] de la part de yuewen.fang [[email protected]<mailto:[email protected]>] Envoyé : samedi 12 septembre 2015 20:42 À : pw_forum Objet : Re: [Pw_forum] magnetic anisotropy calculation using fully-relativistic PPs Hi, Yun-Peng, Thanks for your feedback. It depends on the matter which you are interested in. I think this paper (Phys. Rev. B 86, 085135 (2012)) can help you. Bests Fang ________________________________ Yue-Wen FANG, PhD candidate East China Normal University<http://english.ecnu.edu.cn/> < peter<mailto:[email protected]>> 2015-09-13 02:16:28 wrote: Thank you for your suggestions! I tried using a small mixing beta (0.1~0.2), and tried using reasonable cutoff energies (ecutwfc=50, ecutrho=500), now the convergence is much better than before (converged down to 10^-6 Ry). Another question is, I can find ultra-soft and PAW pseudopotentials, which one is better for spin-orbit calculations? I am using PBE XC functional. best, Yun-Peng On 09/11/2015 08:08 PM, yuewen.fang wrote: Dear Yun-Peng, Plz try to decrease mixing and perform some convergence tests for your cutoff energy to remove the oscillation of the energy! In addition, this oscillation could also be caused by the unreasonable smearing methods for metals. Bests Fang ________________________________ Sent from YoMail<http://www.yomail.com/?utm_source=signature> < Peter Cybertron<mailto:[email protected]>> 2015-09-12 03:10:31 wrote: Hi, I am working in University of Florida as a postdoc. I am exploring the spin-orbital calculations using pwscf, and I encounter a very slow convergence like this: > grep estimated scf.out estimated scf accuracy < 0.00000004 Ry ... (100 similar lines) estimated scf accuracy < 0.00000003 Ry > grep "total energy" scf.out ... total energy = -3667.91077719 Ry total energy = -3667.91078176 Ry total energy = -3667.91077642 Ry total energy = -3667.91078300 Ry Although the convergence of total energy seems OK (down to 0.00001 Ry ~ 0.0001 eV = 0.1 meV), I still feel uncomfortable since I never encounter such a problem without spin-orbit interactions. I downloaded the ultrasoft and PAW pseudopotentials from PSLib and I am using the PBE flavor of XC functional. The system I am studying is a two dimensional magnetic insulator. The parameters I am using are: constrained_magnetization = 'total direction' fixed_magnetization(3) = 0.0 lambda = 0.2 ecutwfc = 30.0 , ecutrho = 300.0 , occupations = 'smearing' , degauss = 0.005, smearing = 'mv' , nosym=.true. mixing_mode = 'local-TF' , mixing_beta = 0.9 , diagonalization = 'david' , Which parameter on earth keep my calculations non-converged? Best, Yun-Peng _______________________________________________ Pw_forum mailing list [email protected]<mailto:[email protected]> http://pwscf.org/mailman/listinfo/pw_forum _______________________________________________ Pw_forum mailing list [email protected]<mailto:[email protected]>http://pwscf.org/mailman/listinfo/pw_forum _______________________________________________ Pw_forum mailing list [email protected]<mailto:[email protected]> http://pwscf.org/mailman/listinfo/pw_forum
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