[Wien] Simultaeneous optimization of atomic coordinates with lattice parameters
shamik chakrabarti
shamik15041981 at gmail.com
Wed Aug 12 16:00:08 CEST 2020
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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>>>>
>>>
>>>
>>> --
>>> 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
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