Re: [Wien] Question regarding volume expansion-contraction after extraction of Li ions

[Peter Blaha]

The options "optimize vol, c/a or b/a" are "special" options for certain 
properties, but for sure a sequential optimization along these lines 
does NOT give the minimum a,b,c.


In your case it seems you should use option [6], vary a,b,c.

Furthermore: it is vital, that you optimize internal coordinates (MSR1a 
or min_lapw) for each of these steps (modify the resulting script).


When you are talking about Fe2+,3+; you have to think whether GGA+U is 
necessary ??


On 03/10/2014 06:32 AM, shamik chakrabarti wrote:

Dear wien2k users,

  We have simulated structural, elcetronic properties and cathode
characteristics (in terms of voltage) of a Li based material. When we
extract some Li ions from the parent compounds and optimize its volume
and lattice parameters, we have obtained a decrements in volume. This
decrements has been followed from the concern that Fe+2 ion get oxidized
in Fe+3 ions in the delithiated compounds & hence there is an decrements
in Fe-O bond length in comparison to the parent (lithiated) one.

However, simulation report on the same compound, computed in VASP, has
shown that there is actually an expansion of volume after Li extraction.
This expansion occurs as when Li ions are taken out from the parent
materials there is a decrements of attraction between two layers
connected with Li ions previously. At least this is the explanation
given by earlier researchers.

we optimize the material and its Li extracted counterpart by following
the methods:
(1) volume optimization by keeping a:b:c constant, (2) optimizing c/a
ratio and (3) optimizing b/a ratio

we have taken lattice parameters after (3) rd operation (optimization)
and calculated  DOS and voltage.

we have also seenthat after 3rd optimization

(1) there is an increment in b/a ratio in the delithiated part than in
the lithiated part in agreement with VASP
(2) However, unit cell volume of the de-lithiated part is less than the
lithiated compound due to more dominant reduction of Fe-O bond lengths
in comparison to the increment of layer-layer separation due to Li ion
extractions in our calculation.

Now my queries are:

(1) Is the reduction of Fe-O bond length after Li extraction is more
than the decrements of layer-layer separation in FPLAPW calculation?...&
that's why we have achieved decrements of volume instead of increments
as obtained in VASP?

(2) Whether this difference came out from some inherent fact of FPLAPW
and PAW (VASP) approach?

(3) Whether this is the limitation of the wien2k code itself?

(4) Or, whether our methodology of calculation by first volume
optimization & then further optimizing c/a and b/a rationis actually
a wrong path...& we should choose some other way for lattice parameter
optimization after Li extraction.

Sorry for such a long email. However, the answer of these queries are
very necessary for our further research and I believe, this discussion
will help the community as a whole.

Thanks in advance,

with regards,

--
Shamik Chakrabarti
Senior Research Fellow
Dept. of Physics & Meteorology
Material Processing & Solid State Ionics Lab
IIT Kharagpur
Kharagpur 721302
INDIA


___
Wien mailing list
Wien@zeus.theochem.tuwien.ac.at
http://zeus.theochem.tuwien.ac.at/mailman/listinfo/wien
SEARCH the MAILING-LIST at:  
http://www.mail-archive.com/wien@zeus.theochem.tuwien.ac.at/index.html



--

  P.Blaha
--
Peter BLAHA, Inst.f. Materials Chemistry, TU Vienna, A-1060 Vienna
Phone: +43-1-58801-165300 FAX: +43-1-58801-165982
Email: bl...@theochem.tuwien.ac.atWWW: 
http://info.tuwien.ac.at/theochem/

--
___
Wien mailing list
Wien@zeus.theochem.tuwien.ac.at
http://zeus.theochem.tuwien.ac.at/mailman/listinfo/wien
SEARCH the MAILING-LIST at:  
http://www.mail-archive.com/wien@zeus.theochem.tuwien.ac.at/index.html

[Wien] Question regarding volume expansion-contraction after extraction of Li ions

[shamik chakrabarti]

Dear wien2k users,

 We have simulated structural, elcetronic properties and cathode
characteristics (in terms of voltage) of a Li based material. When we
extract some Li ions from the parent compounds and optimize its volume and
lattice parameters, we have obtained a decrements in volume. This
decrements has been followed from the concern that Fe+2 ion get oxidized in
Fe+3 ions in the delithiated compounds & hence there is an decrements in
Fe-O bond length in comparison to the parent (lithiated) one.

However, simulation report on the same compound, computed in VASP, has
shown that there is actually an expansion of volume after Li extraction.
This expansion occurs as when Li ions are taken out from the parent
materials there is a decrements of attraction between two layers connected
with Li ions previously. At least this is the explanation given by earlier
researchers.

we optimize the material and its Li extracted counterpart by following the
methods:
(1) volume optimization by keeping a:b:c constant, (2) optimizing c/a ratio
and (3) optimizing b/a ratio

we have taken lattice parameters after (3) rd operation (optimization) and
calculated  DOS and voltage.

we have also seenthat after 3rd optimization

(1) there is an increment in b/a ratio in the delithiated part than in the
lithiated part in agreement with VASP
(2) However, unit cell volume of the de-lithiated part is less than the
lithiated compound due to more dominant reduction of Fe-O bond lengths in
comparison to the increment of layer-layer separation due to Li ion
extractions in our calculation.

Now my queries are:

(1) Is the reduction of Fe-O bond length after Li extraction is more than
the decrements of layer-layer separation in FPLAPW calculation?...& that's
why we have achieved decrements of volume instead of increments as obtained
in VASP?

(2) Whether this difference came out from some inherent fact of FPLAPW and
PAW (VASP) approach?

(3) Whether this is the limitation of the wien2k code itself?

(4) Or, whether our methodology of calculation by first volume optimization
& then further optimizing c/a and b/a rationis actually a wrong
path...& we should choose some other way for lattice parameter optimization
after Li extraction.

Sorry for such a long email. However, the answer of these queries are very
necessary for our further research and I believe, this discussion will help
the community as a whole.

Thanks in advance,

with regards,

-- 
Shamik Chakrabarti
Senior Research Fellow
Dept. of Physics & Meteorology
Material Processing & Solid State Ionics Lab
IIT Kharagpur
Kharagpur 721302
INDIA
___
Wien mailing list
Wien@zeus.theochem.tuwien.ac.at
http://zeus.theochem.tuwien.ac.at/mailman/listinfo/wien
SEARCH the MAILING-LIST at:  
http://www.mail-archive.com/wien@zeus.theochem.tuwien.ac.at/index.html

Re: [Wien] How to do fixed magnetic moment calculations?

[Peram sreenivasa reddy]

Dear Prof. Peter Blaha,

  Thank you very much for your replay and suggestion.

  Your doubt is correct. I got the exact similar ones.

I will change the case.insp file and i will get back to you once i got the
result.

Thanking you.



On Fri, Mar 7, 2014 at 9:28 PM, Peter Blaha wrote:

> I very much doubt that you got the "same" bands, probably you got "very
> similar" ones.
>
> Anyway, runfsm uses 2 different fermi-energies for up and dn and you
> should plug in these two fermi energies into case.insp if you want to see
> the "enhanced splitting".
>
>
> On 03/07/2014 08:19 AM, Peram sreenivasa reddy wrote:
>
>> Dear Prof. Peter Blaha,
>>
>> I initiated the calculations in magnetic case.
>>
>> After initiating the calculations i gave run command as "runfsm_lapw -m
>> 1.95 -ec 0.01".
>>
>> In my case.scf file i got the magnetic moment value as 1.95 bohr
>> magneton as i was gaven in the run command.
>>
>> After this step i continued for band like as follows
>>
>> x lapw1 -band -up
>>
>> x lapw1 -band -dn
>>
>> x irrep -up
>>
>> x irrep -dn
>>
>> x spaghetti -up
>>
>> x spaghetti -dn
>>
>> I got the same band results as previous one with run command "runsp_lapw
>> -ec 0.01".
>>
>> How can i proceed further?
>>
>> Thank you in advance .
>>
>>
>>
>> On Thu, Mar 6, 2014 at 10:11 AM, Peram sreenivasa reddy
>> mailto:peramsreeni...@gmail.com>> wrote:
>>
>> Dear Peter Blaha,
>>
>> Thank you very much for your replay. I will get back to you with my
>> results after using this command.
>>
>> Thanking you ..
>>
>>
>>
>> On Wed, Mar 5, 2014 at 11:59 AM, Peter Blaha
>> mailto:pbl...@theochem.tuwien.ac.at>>
>>
>> wrote:
>>
>> runfsm -m XX
>>
>> Am 05.03.2014 06:56, schrieb Peram sreenivasa reddy:
>>
>> Dear Users,
>>I want to fix the magnetic moment to my
>> system. How to do these fixed magnetic moment calculations?.
>>
>> Thank you very much in advance.
>>
>>
>>
>>
>>
>> _
>> Wien mailing list
>> w...@zeus.theochem.tuwien.ac.__at
>> 
>> http://zeus.theochem.tuwien.__ac.at/mailman/listinfo/wien
>>
>> 
>> SEARCH the MAILING-LIST at:
>> http://www.mail-archive.com/__wien@zeus.theochem.tuwien.ac._
>> _at/index.html
>> > at/index.html>
>>
>>
>> --
>> --__---
>>
>> Peter Blaha
>> Inst. Materials Chemistry, TU Vienna
>> Getreidemarkt 9, A-1060 Vienna, Austria
>> Tel: +43-1-5880115671
>> Fax: +43-1-5880115698
>> email: pbl...@theochem.tuwien.ac.at
>> 
>> --__---
>> _
>> Wien mailing list
>> w...@zeus.theochem.tuwien.ac.__at
>> 
>> http://zeus.theochem.tuwien.__ac.at/mailman/listinfo/wien
>>
>> 
>> SEARCH the MAILING-LIST at:
>> http://www.mail-archive.com/__wien@zeus.theochem.tuwien.ac._
>> _at/index.html
>> > at/index.html>
>>
>>
>>
>>
>>
>>
>>
>>
>>
>>
>>
>>
>> ___
>> Wien mailing list
>> Wien@zeus.theochem.tuwien.ac.at
>> http://zeus.theochem.tuwien.ac.at/mailman/listinfo/wien
>> SEARCH the MAILING-LIST at:  http://www.mail-archive.com/
>> wien@zeus.theochem.tuwien.ac.at/index.html
>>
>>
> --
>
>   P.Blaha
> --
> Peter BLAHA, Inst.f. Materials Chemistry, TU Vienna, A-1060 Vienna
> Phone: +43-1-58801-165300 FAX: +43-1-58801-165982
> Email: bl...@theochem.tuwien.ac.atWWW: http://info.tuwien.ac.at/
> theochem/
> --
>
> ___
> Wien mailing list
> Wien@zeus.theochem.tuwien.ac.at
> http://zeus.theochem.tuwien.ac.at/mailman/listinfo/wien
> SEARCH the MAILING-LIST at:  http://www.mail-archive.com/
> wien@zeus.theochem.tuwien.ac.at/index.html
>
___
Wien mailing list
Wien@zeus.theochem.tuwien.ac.at
http://zeus.theochem.tuwien.ac.at/mailman/listinfo/wien
SEARCH the MAILING-LIST at:  
http://www.mail-archive.com/wien@zeus.theochem.tuwien.ac.at/index.html