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

[shamik chakrabarti]

Dear All,
              I am sending the LiNiNbO4_ca_initial.struct file which is
obtained after volume optimization with a:b:c =constant. Also I am sending
LiNiNbO4_ba_initial.struct which is obtained after c/a optimization with
constant volume and b/a. Both the structures are showing same unit cell
volume as ~ 2144 bohr^3 as I have obtained in my calculation where as the
printed volume in the w2web page obtained after c/a optimization is
2058.7690 bohr^3 which is different than the actual optimized volume we
have obtained. Please comment on this.

with regards,


On Sat, 13 Jun 2020 at 02:03, Tomas Kana <kana at seznam.cz> wrote:

>
> Zpět
> Dnes 22:15Tomas KanaKomu:wien at zeus.theochem.tuwien.ac.at
> Re: [Wien] Volume has changed during running optimization of c/a with
> constant volume & b/a
> Dear Shamik, If I understand you correctly then I suggest to visualise
> better your energy-volume curve. Try this (it works for me): 1. Keep c/a
> and b/a experimental ones and run x optimize option 1 and make an
> energy-volume curve by modifying he option save_lapw -d ../$i  $i in the
> file optimize.job that is produced by x optimize. 2. For each separated
> directory run_lapw and collect all the scf files to one one directory and
> visualise the resulting energy-volume curve by  eplot -t vol 3. In each
> separated directory optimize c/a  at constant volume and b/a. Again
> collect all scf files and visualise both "experimental" and "relaxed"
> energy volume curve in one plot. You will probably note and understand the
> difference between the two mimimums. 4. Do the same optimization for b/a at
> constant volume and c/a and draw the three energy-volume curves together.
> Their minima could again differ. Repeat 3 and 4 until the resulting e-v
> curve does not substantially differ from the preceding one. Alternatively
> you may use the package OrthoOpt from wien2k goodies.
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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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