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

Fri Jun 12 18:15:19 CEST 2020

Dear Shamik,

I think it would be 
aNew * bNew * cNew = volumeNew 
a * b * c = volumeOriginal 
bNew/aNew = bA = b/a 
cNew/aNew = cA = c/a 

volumeNew = aNew * (Aew * bA) * (aNew * cA) = 
= aNew^3 * bA*cA 
volume = a * (a * bA) * (a * cA) = a^3 * bA * cA 
volumeNew / volume = (aNew/a)^3 
If this is your x-parameter, then I was 
originally thinking that you have forgotten 
to take into account the cAnew and bAConst dividing 
the original volume when optimizing c/a at constant b/a 
and volume in the next step. 
But now, looking at your structure file I suspect this: 
Your lattice parameters a and b from your structure 
file are very similar. 
The ratio bNew / aNew in your optimized structure file is 
11.699299 bohr / 11.264662 bohr = 1.038584
This is rather close to the ratio of your volumes before 
and after c/a optimization at constant volume: 
2146.485 bohr^3 / 2058.7690 bohr^3 = 1.042606
Perhaps, if you tried to optimize 
c/a at constant volume and constant b/a using x optimize
you might do a misprint and choose option 2 in x optimize instead of option 3. Is this possible? But then, you should 
have a and b the same in your structure file (and you have not) However, the a and b  could become again different after applying another b/a optimization at constant volume and c/a. 
Or, if you did it manually you could somehow interchange 
a and b lattice parameters when recalculating them. Is this 
possible? 
HTH 
Tomas 

---------- 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 17:33:19

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

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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-- 

Peter Blaha

Inst.Materials Chemistry

TU Vienna

Getreidemarkt 9

A-1060 Vienna

Austria

+43-1-5880115671

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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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