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

[Gavin Abo]

By volume on the w2web page, are you referring to the estimated actual 
optimized volume (or lattice constants) given by the Equation of State 
fit(s) such as by Birch-Murnaghan seen in the post at [1]? As you have 
probably read in the post [2] or noticed, the case.struct files from "x 
optimize" do not contain the structure parameters for the estimated 
actual optimized volume. Therefore, you have to take the fitted 
structure parameters and enter them in StructGen for example to create 
the optimized struct file unless you specified a very dense set of 
structure changes in "x optimize" around the energy minimum, usually 
pinpointed from a previous "x optimize" using a course set of structure 
changes, in which taking the struct file closest to the minimum 
approximately gives the same parameters as that from a fit.  There was a 
previous example given for one of the cases [3] that might help with 
other cases.  If you know Fortran, I think it was 
SRC_optimize/optimize.f that contained the code on how the input 
structure parameters are changed by "x optimize" to become the output 
struct files.  It your looking for fit results outside of w2web, those 
seem to be found in the case.outputeos* files [4-6]. Hopefully [1-12] 
will be helpful to you on the topic of structure optimization.

[1] 
https://www.mail-archive.com/wien@zeus.theochem.tuwien.ac.at/msg16043.html
[2] http://zeus.theochem.tuwien.ac.at/pipermail/wien/2011-June/014835.html
[3] 
https://www.mail-archive.com/wien@zeus.theochem.tuwien.ac.at/msg10071.html
[4] 
https://www.mail-archive.com/wien@zeus.theochem.tuwien.ac.at/msg15957.html
[5] 
https://www.mail-archive.com/wien@zeus.theochem.tuwien.ac.at/msg08565.html
[6] 
https://www.mail-archive.com/wien@zeus.theochem.tuwien.ac.at/msg14372.html
[7] 
https://www.mail-archive.com/wien@zeus.theochem.tuwien.ac.at/msg02002.html
[8] 
https://www.mail-archive.com/wien@zeus.theochem.tuwien.ac.at/msg06932.html
[9] 
https://www.mail-archive.com/wien@zeus.theochem.tuwien.ac.at/msg02859.html
[10] 
https://www.mail-archive.com/wien@zeus.theochem.tuwien.ac.at/msg09397.html
[11] 
https://www.mail-archive.com/wien@zeus.theochem.tuwien.ac.at/msg17074.html
[12] 
https://www.mail-archive.com/wien@zeus.theochem.tuwien.ac.at/msg17347.html

On 6/12/2020 11:14 PM, shamik chakrabarti wrote:
> 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,
>