[Wien] Simultaeneous optimization of atomic coordinates with lattice parameters
Laurence Marks
laurence.marks at gmail.com
Wed Aug 12 16:07:26 CEST 2020
>From a Google search "*Acceptable results* means a variance of less than
plus or minus two (2) standard deviations".
Remembering that (depending upon functional) there is a nett
contraction/expansion, what is the standard deviation of your measurements
and is your calculation within two sigma ?
(And don't email back asking if it is, be a scientist and answer it
yourself.)
On Wed, Aug 12, 2020 at 9:00 AM shamik chakrabarti <shamik15041981 at gmail.com>
wrote:
> Dear Prof. Laurence Marks Sir,
>
> Thank you for your email.
> Sir, we have obtained the following results by using the above procedure;
>
> Expt. Theory
> a=12.134 a=11.8071
> b= 3.87 b=3.8838
> c= 11.23 c=10.9285
>
> Whether these are acceptable results?
>
> with regards,
>
>
> On Wed, 12 Aug 2020 at 18:53, Laurence Marks <laurence.marks at gmail.com>
> wrote:
>
>> I have an impression that you have asked before about optimization, in
>> fact many times!
>>
>> A question you should ask yourself is what are you trying to achieve? DFT
>> is not a perfect theory, and while you can improve the agreement with
>> experiment using better (and slower) methods, in general experiment is more
>> accurate.
>>
>> If your calculations are close to experiment, e.g. atoms at positions
>> maybe 0.01 Angers off, that is all you can expect.
>>
>> If, for instance, the positions are 0.1 Angers off, and/or it is a metal
>> whereas in experiment it is an insulator, then something is very wrong. No
>> amount of lattice optimization is going to help.
>>
>> So, my question to you is are you killing defenseless electrons in a
>> quest to overfit data, or is there a reason?
>>
>> _____
>> 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 Wed, Aug 12, 2020, 08:11 shamik chakrabarti <shamik15041981 at gmail.com>
>> wrote:
>>
>>> Also after obtaining the c/a optimized struct file with optimized
>>> lattice parameter & nearly optimized atomic coordinates for a hexagonal
>>> system I do a force minimization by keeping the lattice parameter intact
>>> (as obtained from c/a optimization curve). Whether this will give a wrong
>>> minima?
>>>
>>> with regards,
>>>
>>> On Wed, 12 Aug 2020 at 18:17, shamik chakrabarti <
>>> shamik15041981 at gmail.com> wrote:
>>>
>>>> Dear Prof. Blaha,
>>>>
>>>> I have done some calculations by keeping both lines
>>>> active. What it does;
>>>> (!) It runs first runsp_lapw -ec 0.0001 for a given struct file
>>>> (2) After getting the energy convergence, it does the force
>>>> minimization for the given structure & saves the successive struct files as
>>>> case_i.scf for i=1,2....
>>>> (3) after getting the force optimized structure it saves the optimized
>>>> struct files in case....._default.struct.
>>>>
>>>> What I do I take the optimized struct file which is near the minima
>>>> i.e, say case_coa____-5.00 _default .struct for next calculation & put the
>>>> lattice parameters in this file by calculating it by hand from c/a
>>>> optimized curve.
>>>>
>>>> Is this give the wrong minimum?
>>>>
>>>> Looking forward to your response in this regard.
>>>>
>>>> with regards,
>>>>
>>>> On Wed, 12 Aug 2020 at 17:59, Peter Blaha <pblaha at theochem.tuwien.ac.at>
>>>> wrote:
>>>>
>>>>> You certainly don't want both lines active.
>>>>>
>>>>> For a simultaneous optimization of internal coordinates, the
>>>>> recommended
>>>>> command in optimize.job is to add -min to the run-command:
>>>>>
>>>>> runsp_lapw -nlvdw -fc 1 -ec 0.001 -min
>>>>>
>>>>> An older alternative (usually not recommended) is:
>>>>>
>>>>> min -I -j "runsp_lapw -nlvdw -I -fc 1.0 -i 40 "
>>>>>
>>>>>
>>>>> On 8/12/20 11:03 AM, shamik chakrabarti wrote:
>>>>> > Dear Wien2k users,
>>>>> > I have edited the optimized.job by
>>>>> > uncommenting the following two lines for running simultaneous
>>>>> > optimization of atomic coordinates with a,b,c:
>>>>> >
>>>>> > runsp_lapw -nlvdw -ec 0.0001
>>>>> >
>>>>> > min -I -j "runsp_lapw -nlvdw -I -fc 1.0 -i 40 "
>>>>> >
>>>>> > Is this method is correct?
>>>>> >
>>>>> > Looking forward to hearing from you.
>>>>> >
>>>>> > Thanks in advance
>>>>> >
>>>>> > with regards,
>>>>> >
>>>>> > --
>>>>> > Dr. Shamik Chakrabarti
>>>>> > Research Fellow
>>>>> > Department of Physics
>>>>> > Indian Institute of Technology Patna
>>>>> > Bihta-801103
>>>>> > Patna
>>>>> > Bihar, India
>>>>> >
>>>>> > _______________________________________________
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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
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>>>>>
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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
>>> _______________________________________________
>>> Wien mailing list
>>> Wien at zeus.theochem.tuwien.ac.at
>>>
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>>>
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>>
>
>
> --
> Dr. Shamik Chakrabarti
> Research Fellow
> Department of Physics
> Indian Institute of Technology Patna
> Bihta-801103
> Patna
> Bihar, India
> _______________________________________________
> Wien mailing list
> Wien at zeus.theochem.tuwien.ac.at
>
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>
--
Professor Laurence Marks
Department of Materials Science and Engineering
Northwestern University
www.numis.northwestern.edu
Corrosion in 4D: www.numis.northwestern.edu/MURI
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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