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

Fri Jun 12 17:16:31 CEST 2020

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
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