[Wien] optimization of an orthorhombic cell

[Dr. K. C. Bhamu]

Thank you very much for a hint.

I thought the value obtained from "VARY C/A RATIO with CONSTANT VOLUME and
B/A (orthorh lattice)"  are well optimised then why I do need to optimise
all of them again.


Now I see, B/A scaling will give us optimised b, then C/A scaling will give
us optimised C and finally optimised v(=a*b*c) will give us optimised "a".
Using optimised a,b,c structure relaxation will be done.


I should be fine to optimised an orthorhombic cell.   Is it?




Regards
Bhamu

On Fri, Oct 13, 2017 at 11:18 AM, Fecher, Gerhard <fecher at uni-mainz.de>
wrote:

> you have three quantities V=a*b*c, b=a*(b/a) and c=a*(c/a)
> so what is the problem ?
>
> Ciao
> Gerhard
>
> DEEP THOUGHT in D. Adams; Hitchhikers Guide to the Galaxy:
> "I think the problem, to be quite honest with you,
> is that you have never actually known what the question is."
>
> ====================================
> Dr. Gerhard H. Fecher
> Institut of Inorganic and Analytical Chemistry
> Johannes Gutenberg - University
> 55099 Mainz
> and
> Max Planck Institute for Chemical Physics of Solids
> 01187 Dresden
> ________________________________________
> Von: Wien [wien-bounces at zeus.theochem.tuwien.ac.at] im Auftrag von Dr. K.
> C. Bhamu [kcbhamu85 at gmail.com]
> Gesendet: Freitag, 13. Oktober 2017 00:42
> An: A Mailing list for WIEN2k users
> Betreff: Re: [Wien] optimization of an orthorhombic cell
>
> Dear List,
>
>
> Could you please help me to get optimize lattice parameters from the
> procedure that I followed as mentioned below:
>
>
>
> The procedure is a four-step task what I am following:
>
> The original lattice parameters were: a, b, c=16.763005, 24.803600,
> 16.320431  >> vol 6785.64777697697 bohr^3.
>
>
> 1.   VARY C/A RATIO with CONSTANT VOLUME and B/A (orthorh lattice)
>
> getting below optimized data:
>  ==========================================================
> Lowest point on X-axis is =  -1.615800
> Minimum value of B/A is =     1.455755
> Minimum value of ENE is =   -339059.104498 Ry
>  ==========================================================
> Value of A is =     16.85428 bohr  ;    8.91890 Ang
> Value of B is =     24.53569 bohr  ;   12.98373 Ang
> Value of C is =     16.40929 bohr  ;    8.68342 Ang
>  ==========================================================
> Initial value of  B/A is =          1.479663
> Conv. Unit Cell Vol =  6785.7557 bohr^3 ; **********Ang^
>
>
> 2.  Volume optimization using option 1 in "x optimize" and then
> calculating new volume from eplot option.
>
>
> Query: Step two is giving optimized volume but I do not know how to
> calculate lattices parameters from a single volume
> value for the next step "VARY C/A RATIO with CONSTANT VOLUME and B/A
> (orthorh lattice)"?
>
>
> The original cell volume and lattice parameters are mentioned at the
> beginning.
>
> and the new volume from step two is: 6815.3427 bohr^3
>
>
>
> The above same query is for the remaining process:
>
> 3. optimization of C/A
>
> 4. optimization of V.
>
>
> *5 At the final step I will do structural relaxation (min_.....).
>
>
> Could you please advice me how to proceed?
>
>
>
> Kind regards,
> Bhamu
>
>
>
>
>
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