[Wien] Calculation spin-orbit coupling with two different approach gives different results

[Santu Baidya]

Dear Prof. Laurence Marks,

    Thank you very much for your suggestion. I just checked "grep :MVORD
".  It gives

:MVORD  NDM  150 L1   2.800091E-06 %   5.2649E-02  when started from
collinear ground state.

Same estimate "grep :MVORD " gives

:MVORD  NDM  150 L1   1.028089E-05 %   1.3122E-01 when started from scratch.

So for both cases :MVORD is less than 1% ?

Please enlighten this little more.



Thanking you and with regards,

Santu Baidya













On 23 November 2015 at 19:31, Laurence Marks <L-marks at northwestern.edu>
wrote:

> Let me add one small thing to what Peter said. Be careful to check that
> you truly have a converged density. It is possible for the scf iterations
> to converge to a trap where the density (:DIS etc) is converged but the
> orbital terms (:MVORD) are not self-consistent. I would estimate that for a
> self-consistent orbital potential :MVORD should be less than 1%. It can be
> necessary to take some measures to climb out of local traps like this, for
> instance by doing "echo 0.1 > .pratt" to force a Pratt step to be included.
> This can be important when -so is included, and in a few cases when it is
> not.
>
> On Mon, Nov 23, 2015 at 7:45 AM, Santu Baidya <santubaidya2009 at gmail.com>
> wrote:
>
>> Dear Prof. Blaha,
>>
>>   Thank you very much for you reply on this. Actually I did relax the
>> structure under GGA+U approximation. Then took two approaches.  In one case
>> I did SCF calculation under GGA+U with relaxed structure  and added SOC
>> afterthat. In other case I took relaxed structure and did GGA+U+SOC
>> calculation.
>> Which gave me two different electronic structure for the same relaxed
>> structure.
>>
>> So I have to take lowest energy structure.
>>
>> Thanking you and regards,
>>
>> Santu Baidya
>>
>>
>>
>>
>>
>> On 23 November 2015 at 18:58, Peter Blaha <pblaha at theochem.tuwien.ac.at>
>> wrote:
>>
>>> It is well know that GGA+U calculations can end up in different states
>>> (see previous posts).
>>>
>>> If you have used the same parameters, you should use the total energies
>>> of the two calculations and the one with lower energy should be the better
>>> one (but not necessarily the best !)
>>>
>>> In any case, I always recommend:
>>>
>>> First do a standard GGA calculation (also check forces, if they are
>>> small).
>>> Then add SO and do a GGA+SO calculation (if you really have heavy
>>> elements?)
>>> x lapwdm -up -so      to generate density matrices
>>>
>>> and finally add the "U" and do   GGA+so+U
>>>
>>> There is, however, no guarantee that you find the lowest energy ground
>>> state !  Sometimes it is good to start with a smaller U-value than
>>> anticipated.
>>> Sometimes you may do a structure relaxation at the GGA-level and use
>>> this structure,
>>> or a structure relaxation at GGA+U (no SO).
>>>
>>> If SO is not a major effect, I'd first do everything without SO.
>>>
>>> -------------------
>>> From these advices you can see that there is not a unique and save way,
>>> which works in all cases.
>>>
>>>
>>>
>>> On 11/23/2015 12:10 PM, Santu Baidya wrote:
>>>
>>>> Dear Prof. Blaha and wien2k users,
>>>>
>>>>       I use wien2k version WIEN2k_14.1. Recently I did spin-orbit
>>>> coupling calculation under GGA+U+SOC approximation with two different
>>>> approaches- one starting from collinear ground state and another
>>>> starting from scratch (random wavefunction). Two approaches give me
>>>> completely different results -metal and insulator.
>>>>
>>>> Please tell me which approach should I accept as solution.
>>>>
>>>> I look forward to get reply.
>>>>
>>>> Thanking you,
>>>>
>>>> Santu Baidya
>>>> University of Duisburg-Essen
>>>> Duisburg
>>>>
>>>>
>>>>
>>>>
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>>>>
>>> --
>>>
>>>                                       P.Blaha
>>>
>>> --------------------------------------------------------------------------
>>> Peter BLAHA, Inst.f. Materials Chemistry, TU Vienna, A-1060 Vienna
>>> Phone: +43-1-58801-165300             FAX: +43-1-58801-165982
>>> Email: blaha at theochem.tuwien.ac.at    WIEN2k: http://www.wien2k.at
>>> WWW:   http://www.imc.tuwien.ac.at/staff/tc_group_e.php
>>>
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>>
>>
>
>
> --
> Professor Laurence Marks
> Department of Materials Science and Engineering
> Northwestern University
> www.numis.northwestern.edu
> Corrosion in 4D: MURI4D.numis.northwestern.edu
> Co-Editor, Acta Cryst A
> "Research is to see what everybody else has seen, and to think what nobody
> else has thought"
> Albert Szent-Gyorgi
>
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