[Wien] Volume has changed during running optimization of c/a with constant volume & b/a

[shamik chakrabarti]

Another thing is that from volume optimization the unit cell volume is
coming as 1073.2425 bohr^3 which get doubles when we consider the volume of
a conventional cell to become 2146.485 bohr^3  while the printed volume of
a conventional unit cell after c/a optimization is coming as 2058.7690
bohr^3 ; Why is this discrepancy? Is it that the conventional cell volume
about 1.9183 times the unit cell volume & not as I have assumed. I am
sending the fully optimized struct (according to my calculation) file for
your consideration.

with regards,

On Fri, 12 Jun 2020 at 20:46, shamik chakrabarti <shamik15041981 at gmail.com>
wrote:

> Dear Tomas,
>
>                Can you please elaborate how to know a', b' and c' (the
> final lattice parameters) from a unit cell volume optimization with a:b:c =
> constant (where a, b, c are initial lattice parameters) ?
>
> with regards,
>
> On Fri, 12 Jun 2020 at 17:15, Tomas Kana <kana at seznam.cz> wrote:
>
>> Dear Shamik,
>> Ok, I undestand your point.
>> But anyway, I think, that the problem comes
>> from your equation.
>> If you want to relax c/a with constant volume and
>> constant b/a then I would prefer these eqations:
>> original c/a = cAoriginal
>> b/a = bAconstant
>> new c/a = cAnew
>>
>> original volume a*b*c
>> new volume (the same as original)
>> aNew * bNew * cNew  =
>> aNew * (aNew * bAConstant) * (aNew * cAnew) =
>> aNew^3 * bAConsant*cAnew = original volume
>> You choose your desired cAnew and know0 bAconstant
>> and the original volume.
>> In this way, you obtain the aNew and it is easy to
>> obtain bNew and cNew then. But I still do not understand the
>> parameter x in your eqation.
>> Maybe this could be the source of your error?
>> Hope this helps
>> Tomas
>>
>> Dear Tomas,
>>
>>                  I am sorry to say that you have misunderstood my
>> equation. I have used abcx^3 = a'b'c' where a', b' and c' are the new
>> lattice parameters & not the old a,b,c !!! :)
>>
>>
>> with regards,
>>
>>
>> On Fri, 12 Jun 2020 at 16:31, Tomas Kana <kana at seznam.cz> wrote:
>>
>> Dear Shamik,
>>
>>
>>
>> If you want to keep a constant volume and
>>
>> you use  the equation
>>
>> abcx^3 = 332.934 = abc then only one solution is possible:
>>
>> x = 1.  ax = a, bx = b  cx = c.
>>
>> Your equation does not make sense to me....
>>
>> With best regards
>>
>> Tomas Kana
>>
>>
>>
>>
>>
>> where a, b, c are the initial lattice parameters. From that equation I
>> have found the value of x & then finally multiply x with each lattice
>> parameters to get new lattice parameters as  a* = ax, b*=bx & c*=cx & then
>> put
>>
>>
>>
>>
>>
>> ---------- Původní e-mail ----------
>>
>>
>>
>> Od: shamik chakrabarti <shamik15041981 at gmail.com>
>>
>>
>>
>> Komu: A Mailing list for WIEN2k users <wien at zeus.theochem.tuwien.ac.at>
>>
>>
>>
>> Datum: 12. 6. 2020 10:05:37
>>
>>
>>
>> Předmět: Re: [Wien] Volume has changed during running optimization of c/a
>>
>>  with constant volume & b/a
>>
>>
>>
>> No, I have created a new directory for c/a optimization. I have done
>> the followings,
>>
>>
>>
>> abcx^3 = 332.934 where a, b, c are the initial lattice parameters. From
>> that equation I have found the value of x & then finally multiply x with
>> each lattice parameters to get new lattice parameters as  a* = ax, b*=bx &
>> c*=cx & then put
>>
>>
>>
>> a*,
>>
>>
>>
>> b* &  c* as new inputs for c/a optimization with constant volume in a new
>> directory.
>>
>>
>>
>>
>>
>> with regards,
>>
>>
>>
>>
>>
>> On Fri, 12 Jun 2020 at 13:23, Peter Blaha <pblaha at theochem.tuwien.ac.at>
>> wrote:
>>
>>
>>
>> How did you do:
>>
>>
>>
>>
>>
>>
>>
>> "putting the lattice parameters as input for c/a optimization"   ???
>>
>>
>>
>>
>>
>>
>>
>> If you continue in the previous directory, do you realize that there is
>>
>>
>>
>> a   case_initial.struct   which, if present, is taken a "base struct
>> file".
>>
>>
>>
>>
>>
>>
>>
>> Am 12.06.2020 um 04:12 schrieb shamik chakrabarti:
>>
>>
>>
>> > Dear wien2k users,
>>
>>
>>
>> >
>>
>>
>>
>> >            I am running wien2k 19.1. I have started c/a optimization
>>
>>
>>
>> > with constant volume and b/a for an ABO4 compound. From volume
>>
>>
>>
>> > optimization with a:b:c=constant I have obtained an unit cell volume of
>>
>>
>>
>> > 332.934 Ang^3. While after calculation of lattice parameters and
>> putting
>>
>>
>>
>> > the lattice parameters as input for c/a optimization with *constant
>>
>>
>>
>> > volume* & b/a, the printed unit cell volume is coming as 312.8004
>>  Ang^3.
>>
>>
>>
>> >
>>
>>
>>
>> > Where I am doing wrong?
>>
>>
>>
>> >
>>
>>
>>
>> > 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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>>
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>>
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>>
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>> >
>>
>>
>>
>>
>>
>>
>>
>> --
>>
>>
>>
>> Peter Blaha
>>
>>
>>
>> Inst.Materials Chemistry
>>
>>
>>
>> TU Vienna
>>
>>
>>
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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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>> --
>> 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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