[Wien] Calculation spin-orbit coupling with two different approach gives different results
Laurence Marks
L-marks at northwestern.edu
Mon Nov 23 16:03:08 CET 2015
With those values of :MVORD you are "OK", it is self-consistent. As my
email said large percentage values are an indication of convergence to a
trap.
On Mon, Nov 23, 2015 at 8:26 AM, Santu Baidya <santubaidya2009 at gmail.com>
wrote:
> 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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>>
>
--
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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