[Pw_forum] magnetic anisotropy calculation using fully-relativistic PPs
peter
petercybertron at gmail.com
Sun Sep 13 19:20:10 CEST 2015
Hi Cyrille,
Thank you for sharing this! But is it impossible for the method
implemented in pwscf, or for all methods based on DFT?
best,
Yun-Peng
On 09/13/2015 03:19 AM, BARRETEAU Cyrille wrote:
> 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, SPECBat. 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: cyrille.barreteau at cea.fr /cyrbar at nanotech.dtu.dk
> Web: http://iramis.cea.fr/Pisp/cyrille.barreteau/
> ========================
> ------------------------------------------------------------------------
> *De :* pw_forum-bounces at pwscf.org [pw_forum-bounces at pwscf.org] de la
> part de peter [petercybertron at gmail.com]
> *Envoyé :* samedi 12 septembre 2015 23:33
> *À :* pw_forum at pwscf.org
> *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, SPECBat. 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: cyrille.barreteau at cea.fr /cyrbar at nanotech.dtu.dk
>> Web:
>> <http://iramis.cea.fr/Pisp/cyrille.barreteau/>http://iramis.cea.fr/Pisp/cyrille.barreteau/
>> ========================
>> ------------------------------------------------------------------------
>> *De :* pw_forum-bounces at pwscf.org [pw_forum-bounces at pwscf.org] de la
>> part de yuewen.fang [yuewen.fang at gmail.com]
>> *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:petercybertron at gmail.com>> 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:petercybertron at gmail.com>> 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
>>> Pw_forum at pwscf.org <mailto:Pw_forum at pwscf.org>
>>> http://pwscf.org/mailman/listinfo/pw_forum
>>>
>>>
>>>
>>> _______________________________________________ Pw_forum mailing listPw_forum at pwscf.org
>>> <mailto:Pw_forum at pwscf.org>http://pwscf.org/mailman/listinfo/pw_forum
>>
>>
>>
>> _______________________________________________
>> Pw_forum mailing list
>> Pw_forum at pwscf.org
>> http://pwscf.org/mailman/listinfo/pw_forum
>
>
>
> _______________________________________________
> Pw_forum mailing list
> Pw_forum at pwscf.org
> http://pwscf.org/mailman/listinfo/pw_forum
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.quantum-espresso.org/pipermail/users/attachments/20150913/47f82097/attachment.html>
More information about the users
mailing list