[Wien] Large forces appeared when calculating total energy after structure optimization
Laurence Marks
laurence.marks at gmail.com
Sun Feb 7 09:35:27 CET 2021
Adding Hubbard U will in general change everything, from lattice parameters
to internal parameters. It is impossible for us to guess how much without
specific details about your case. In general you should ALWAYS refine
lattice/internal with the same or very similar parameters/model. The
exception is -so, -hf and the current mGGA.
_____
Professor Laurence Marks
"Research is to see what everybody else has seen, and to think what nobody
else has thought", Albert Szent-Gyorgi
www.numis.northwestern.edu
On Sun, Feb 7, 2021, 02:22 shamik chakrabarti <shamik15041981 at gmail.com>
wrote:
> Dear Prof. Blaha & Gavin,
>
> Sorry to bother you again. I think I have done a
> foolish job by starting with the command .....-i 160 as it will converge
> just at the first or the second cycle without minimizing the forces.
> I have taken into account spin polarization during structure optimization,
> however, I have not taken into account GGA+U for structural optimization. I
> have inserted the U after a converged SCF obtained with spin polarization &
> with the optimized structure.
>
> Looking forward to listen from you.
>
> with regards,
> Dear Prof. Blaha & Gavin,
>
>
>
> On Sun, 7 Feb 2021 at 12:09, shamik chakrabarti <shamik15041981 at gmail.com>
> wrote:
>
>> Dear Prof. Blaha & Gavin,
>>
>> I have checked the final energy obtained
>> (during force minimization) & the energy obtained after an SCF by taking
>> the optimized structure & it is found that the final energy obtained during
>> the force minimization is less (more negative) than the energy obtained
>> during SCF with optimized structure. It seems that that the iteration has
>> found a local minimum. Hence, I have started the SCF again with a command
>> runsp_lapw -dm -orb -NI -fc 1.0 -ec 0.0001 - cc 0.0001 -i 160 (previously
>> the iteration has run for 80 iterations).
>>
>> Is it the correct way to approach it? Looking forward to hearing from you.
>>
>> with best regards,
>>
>> On Sat, 6 Feb 2021 at 22:58, Gavin Abo <gsabo at crimson.ua.edu> wrote:
>>
>>> It might also be worth mentioning that you may need to look into the
>>> details of the structure that you are calculating.
>>>
>>> By that, I'm referring to how optimization of atomic coordinates does
>>> not work on structures were there are no atoms in a free atomic position
>>> and all atoms in the structure are in fixed atomic positions of the
>>> spacegroup, like the example given for NaCl, as described in the
>>> following five links.
>>>
>>> [1] Slide 36:
>>>
>>> http://www.wien2k.at/reg_user/textbooks/WIEN2k_lecture-notes_2013/WIEN2k-getting_started.pdf
>>> <https://urldefense.com/v3/__http://www.wien2k.at/reg_user/textbooks/WIEN2k_lecture-notes_2013/WIEN2k-getting_started.pdf__;!!Dq0X2DkFhyF93HkjWTBQKhk!H3st-fuKu_YysGEjJfIfPBTsF2GDLTad9QoAL6r5eg_1vPF5pUG3HhGkACKbjFHqBWRmhw$>
>>> [2]
>>>
>>> https://www.mail-archive.com/wien@zeus.theochem.tuwien.ac.at/msg20232.html
>>> <https://urldefense.com/v3/__https://www.mail-archive.com/wien@zeus.theochem.tuwien.ac.at/msg20232.html__;!!Dq0X2DkFhyF93HkjWTBQKhk!H3st-fuKu_YysGEjJfIfPBTsF2GDLTad9QoAL6r5eg_1vPF5pUG3HhGkACKbjFFyST5VaA$>
>>> [3]
>>>
>>> https://www.mail-archive.com/wien@zeus.theochem.tuwien.ac.at/msg20213.html
>>> <https://urldefense.com/v3/__https://www.mail-archive.com/wien@zeus.theochem.tuwien.ac.at/msg20213.html__;!!Dq0X2DkFhyF93HkjWTBQKhk!H3st-fuKu_YysGEjJfIfPBTsF2GDLTad9QoAL6r5eg_1vPF5pUG3HhGkACKbjFHXfpI5Xw$>
>>> [4]
>>>
>>> https://www.mail-archive.com/wien@zeus.theochem.tuwien.ac.at/msg02859.html
>>> <https://urldefense.com/v3/__https://www.mail-archive.com/wien@zeus.theochem.tuwien.ac.at/msg02859.html__;!!Dq0X2DkFhyF93HkjWTBQKhk!H3st-fuKu_YysGEjJfIfPBTsF2GDLTad9QoAL6r5eg_1vPF5pUG3HhGkACKbjFE3D0Qong$>
>>> [5]
>>>
>>> https://www.mail-archive.com/wien@zeus.theochem.tuwien.ac.at/msg17074.html
>>> <https://urldefense.com/v3/__https://www.mail-archive.com/wien@zeus.theochem.tuwien.ac.at/msg17074.html__;!!Dq0X2DkFhyF93HkjWTBQKhk!H3st-fuKu_YysGEjJfIfPBTsF2GDLTad9QoAL6r5eg_1vPF5pUG3HhGkACKbjFEgcUINhQ$>
>>>
>>> On 2/6/2021 9:40 AM, Peter Blaha wrote:
>>> > All we can say is that you have done somewhere a mistake.
>>> >
>>> > It is important that you not just "describe" what you did, but list
>>> > the actual commands.
>>> >
>>> > Did you use the same runsp command during "optimization" ?
>>> >
>>> > Could it be that you restarted the final SCF from "scratch" ???
>>> > In DFT+U you might have ended up in a different state when starting
>>> > with dstart densities without *dmat* files.
>>> >
>>> > Compare your total energies of best optimization and the final SCF.
>>> > Which one is lower ?
>>> >
>>> > Am 06.02.2021 um 12:47 schrieb shamik chakrabarti:
>>> >> Dear Wien2k users,
>>> >> I have initially optimized an
>>> >> orthorhombic crystal system structurally (simultaneous
>>> >> optimization of a,b,c & coordinates & then optimization of
>>> >> coordinates again by taking optimized lattice parameters). However,
>>> >> after taking the optimized structure when I simulate the total energy
>>> >> with converged SCF by running the command runsp_lapw -dm -orb -fc 1.0
>>> >> -ec 0.0001 -cc 0.0001, I have found that large forces ~ 40 mRy/a.u.
>>> >> appeared for few atoms.
>>> >>
>>> >> My queries are (a) why this happens? & (b) what is the remedy? (c)
>>> >> whether DOS is reliable in this case?
>>> >>
>>> >> *However, the simulated voltage as calculated from the total energy
>>> >> of the system has been matched with the experiment very well.
>>> >> *
>>> >>
>>> >> Looking forward to hearing from you.
>>> >>
>>> >> with regards,
>>> >> --
>>> >> Dr. Shamik Chakrabarti
>>> >> Research Fellow
>>> >> Department of Physics
>>> >> Indian Institute of Technology Patna
>>> >> Bihta-801103
>>> >> Patna
>>> >> Bihar, India
>>> _______________________________________________
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>>>
>>
>>
>> --
>> Dr. Shamik Chakrabarti
>> Research Fellow
>> Department of Physics
>> Indian Institute of Technology Patna
>> Bihta-801103
>> Patna
>> Bihar, India
>>
>
>
> --
> Dr. Shamik Chakrabarti
> Research Fellow
> Department of Physics
> Indian Institute of Technology Patna
> Bihta-801103
> Patna
> Bihar, India
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