[Wien] Magnetocrystalline anisotropy

[Xavier Rocquefelte]

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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