[Wien] Simultaeneous optimization of atomic coordinates with lattice parameters
Laurence Marks
laurence.marks at gmail.com
Wed Aug 12 15:23:27 CEST 2020
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
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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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