[Wien] Magnetocrystalline anisotropy

Tue Jan 16 17:57:17 CET 2018

Dear Profs. Blaha and Marks,

Thank you for your advices. I have a question regarding your comment on 
the EECE case.

The resulting effective potential of LDA+U and EECE corrections is 
decomposed in vorb files, but I don't understand why the spin-coupling 
file case.vorbud shouldn't appear in the second case.

I have a second question regarding the reading of these orbital 
potential files. We noticed the orb program read only the real part, 
neglecting the imaginary one (Prof. Marks already noticed it in the 
source code). Due to our energy scale which is tiny, could we expect an 
impact of such approximation ? Considering your last comments, it seems 
not due to the execution of the orb program only in lapw1 and not during 
the perturbative procedure.

Thank you by advance.

All the best,

William Lafargue-dit-Hauret

Le 16/01/2018 à 17:05, Xavier Rocquefelte a écrit :
> I was not clear Peter. I clarify the way we proceed.
>
> We do runsp_lapw -eece -p -ec 0.00001 -NI
>
> Then for larger EMAX and kmesh without SO we do :
>
> x lapw1 -up -c -orb
> x lapw1 -dn -c -orb
>
> And for the different magnetization directions we do:
>
> x lapwso -c -up  -orb
> x lapw2 -so -up  -c
> x lapw2 -so -dn  -c
>
>
>
>
> Le 16/01/2018 à 16:58, Peter Blaha a écrit :
>> Hups: If this is true, you are counting the orbital potential twice !
>>
>> -orb should only be present in the lapwso step.
>> (And in fact, the lapw1 steps need to be done just once for the 
>> increased k-mesh; but not when changing the M-direction in case.inso)
>>
>> Please check the presence of case.vorbud. It must not be there for EECE.
>>
>> You could also test Laurence suggestion, running:
>>
>> x lapw1 -up/dn -orb
>> x lapwso -up      (no -orb !!!)
>>
>> and see of it makes a difference.
>>
>> On 01/16/2018 04:52 PM, Xavier Rocquefelte wrote:
>>> Dear Peter
>>>
>>> You are totally correct. We are doing SO non-selfconsistent by using 
>>> a standard procedure for EECE calculations:
>>>
>>> runsp_lapw -eece -p -ec 0.00001 -NI
>>>
>>> and then we estimate the MAE using this non-SCF procedure :
>>>
>>> Increase EMAX in case.in1c - increase kmesh if needed ....
>>>
>>> x lapw1 -up -c -orb
>>> x lapw1 -dn -c -orb
>>> x lapwso -c -up  -orb
>>> x lapw2 -so -up  -c
>>> x lapw2 -so -dn  -c
>>>
>>> Such a procedure was working nicely in previous WIEN2k versions.
>>> Best Regards
>>> Xavier
>>>
>>>
>>>
>>> Le 16/01/2018 à 16:34, Peter Blaha a écrit :
>>>> Hallo Xavier,
>>>>
>>>> Looks rather strange.
>>>>
>>>> Eventually I would have expected problems both, in 16.1 and 17.1 
>>>> (but not 14.2) due to the off-diagonal density matrices. But this 
>>>> should concern ONLY LDA+U, not -eece.
>>>>
>>>> Just to be sure:
>>>>
>>>> I expect you do SO non-selfconsistent, so vorbup/dn(du) files are 
>>>> always the same ??  (just running lapwso and lapw2 -so)
>>>>
>>>> Did you make sure that for -eece -so, case.vorbud is NOT present 
>>>> (from previous LDA+U).
>>>>
>>>> Peter
>>>>
>>>>
>>>> On 01/16/2018 02:50 PM, Xavier Rocquefelte wrote:
>>>>> Here is a document showing the results graphically.
>>>>>
>>>>> https://filesender.renater.fr/?s=download&token=8ac3a214-edfa-4894-fa1f-27aba5a5522f 
>>>>>
>>>>>
>>>>> It really looks like the problem we had before (using bad kmesh).
>>>>>
>>>>> We test it on two different compounds and in both cases WIEN2k_16 
>>>>> gives a correct picture and not WIEN2k_17.
>>>>>
>>>>> We are now comparing the two versions of the code.
>>>>>
>>>>> Regards
>>>>>
>>>>> Xavier
>>>>>
>>>>>
>>>>> Le 16/01/2018 à 12:10, Xavier Rocquefelte a écrit :
>>>>>>
>>>>>> Dear All
>>>>>>
>>>>>> Finally the problem is not completely solved.
>>>>>>
>>>>>> More precisely, when we are doing GGA+SO calculations and using a 
>>>>>> correct kmesh (no temporal symmetry), we obtain a symmetric 
>>>>>> magnetocrystalline anisotropy, namely same MAE along [0 1 0] and 
>>>>>> [0 -1 0].
>>>>>>
>>>>>> In contrast, when we are doing GGA+U+SO or EECE+SO with a correct 
>>>>>> kmesh we still obtain non-symmetric MAE, namely MAE along [0 1 0] 
>>>>>> and [0 -1 0] are different.
>>>>>>
>>>>>> In addition, the so obtained MAE looks similar to the ones 
>>>>>> obtained in GGA+SO with a bad kmesh (including temporal symmetry).
>>>>>>
>>>>>> At this moment, we are checking all the recent modifications in 
>>>>>> SRC_ORB and SRC_LAPW2 related to the manipulation of case.vorbup, 
>>>>>> case.vorbdn and case.vorbud files.
>>>>>>
>>>>>> Surprisingly, the EECE+SO calculations in WIEN2k_16 are 
>>>>>> symmetric, while not in WIEN2k_17.
>>>>>>
>>>>>> Next soon ... I hope.
>>>>>>
>>>>>> Xavier
>>>>>>
>>>>>>
>>>>>> Le 10/01/2018 à 15:10, Xavier Rocquefelte a écrit :
>>>>>>>
>>>>>>> Dear All
>>>>>>>
>>>>>>> The problem is solved and was related to one stupid human mistake.
>>>>>>>
>>>>>>> It was necessary to generate a kmesh without adding inversion 
>>>>>>> (time-inversion symmetry).
>>>>>>> Indeed, as mentionned in the userguide when using kgen program:
>>>>>>>
>>>>>>> # *"add inversion" ?* This is asked only when inversion is NOT 
>>>>>>> present.
>>>>>>>
>>>>>>>   * Say *"YES"* in all cases except when you do *spin-polarized
>>>>>>>     (magnetic) calculations WITH spin-orbit coupling * (this breaks
>>>>>>>     time-inversion symmetry and thus one MUST NOT add inversion
>>>>>>>     symmetry (eigenvalues at +k and -k may be different).
>>>>>>>
>>>>>>> If you properly generate the kmesh for the spin-orbit 
>>>>>>> calculations by doing : x kgen -fbz, then you obtain a symmetric 
>>>>>>> magnetic anisotrop. In conclusion the asymmetry I obtained was 
>>>>>>> due to an improper definition of the kmesh (adding artificially 
>>>>>>> time-inversion).
>>>>>>>
>>>>>>> I want to thank all the participants who answered to my 
>>>>>>> question. It was essential to identify such a mistake which has 
>>>>>>> a huge impact on the results.
>>>>>>>
>>>>>>> Best wishes
>>>>>>>
>>>>>>> Xavier
>>>>>>>
>>>>>>>
>>>>>>>
>>>>>>> Le 10/01/2018 à 10:47, Xavier Rocquefelte a écrit :
>>>>>>>> Dear Lyudmila
>>>>>>>>
>>>>>>>> The fact we have a small angle with axes is expected (also 
>>>>>>>> observed experimentally). It is related to the monoclinic 
>>>>>>>> symmetry of the system which permits it. However, you gave me 
>>>>>>>> an idea that I will test now and comment soon ;)
>>>>>>>>
>>>>>>>> Cheers
>>>>>>>>
>>>>>>>> Xavier
>>>>>>>>
>>>>>>>> Le 10/01/2018 à 10:40, Lyudmila a écrit :
>>>>>>>>> 10.01.2018 13:36, Lyudmila wrote:
>>>>>>>>>> I see in the FM calculation also a slightly non-symmetric 
>>>>>>>>>> curve, isn't it?
>>>>>>>>>
>>>>>>>>> I meant the small angle with axes.
>>>>>>>>>
>>>>>>>>>> Best wishes
>>>>>>>>>> Lyudmila Dobysheva
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>>>>>>>>
>>>>>>>
>>>>>>>
>>>>>>>
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>>>>>>
>>>>>>
>>>>>>
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>>>>>
>>>>>
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-- 
William LAFARGUE-DIT-HAURET
PhD Student
--------------------------------------------------
Institut des Sciences Chimiques de Rennes UMR 6226
Equipe Chimie Théorique Inorganique
Université de Rennes 1 - Campus de Beaulieu
35042 Rennes, France
Building 10B, Desk 211
Phone: +33 (0)2.23.23.57.91
Email: william.lafargue-dit-hauret at univ-rennes1.fr

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