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

Fri Jun 12 13:45:32 CEST 2020

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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