In the scf file you find the volume:
LATTICE = B
:POT : POTENTIAL OPTION EX_PBE EC_PBE VX_PBE VC_PBE
:LAT : LATTICE CONSTANTS= 11.31946 11.79152 16.06778 1.571 1.571 1.571
:VOL : UNIT CELL VOLUME = 1072.31280
and 11.31946 * 11.79152 * 16.06778 / 2 = 1072.312797243878022456
so what is the problem, beside the rounding ?
By the way, what you are doing is "searching for a local minimum" but not an
"optimization"!
You have to find the absolute (!) energy minimum in the a, b, c space
In yourprocedure it might depend on which "minimum energy search" you use to
start, and on the series of seraches.
You can not expect a priori that only one minimum exists in the range
a +- Delta a, b +- Delta b, c +- Delta c
and yo might end up in a "wrong" local minimum.
Further, your structure has free position parameters,
therefore, you have to optimize the positions TOGETHER with the lattice
parameters,
obviously you did not do that, the positions are equal in both files ?
For completeness:
The "Volume optimization" alone has only a physical meaning for cubic systems
(or spherical as most of the equations of states are for the pressure-volume
relation inside earth,
I wonder how they would look like if the earth was a disk, ... or maybe it is
;-).
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-boun...@zeus.theochem.tuwien.ac.at] im Auftrag von shamik
chakrabarti [shamik15041...@gmail.com]
Gesendet: Samstag, 13. Juni 2020 07:14
An: A Mailing list for WIEN2k users
Betreff: Re: [Wien] Volume has changed during running optimization of c/a with
constant volume & b/a
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
<k...@seznam.cz<mailto:k...@seznam.cz>> wrote:
Zpět
[https://i.im.cz/private-avatar/6be7aba869b05ecd061bd77ff52f23ec0d7890f91360a35dc19cfad48b41ad7080ea62f5311a154a/96]Dnes
22:15
Tomas Kana
Komu:
wien@zeus.theochem.tuwien.ac.at<mailto:wien@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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