[Wien] optimization of an orthorhombic cell

[Dr. K. C. Bhamu]

Dear Prof. Marks,

I read your optimization notes for orthorhombic cell and tried to optimize
an orthorhombic cell but I could not obtain an optimization plot.


So I am following the standard procedure as below taken from your
suggestion in the mailing list https://www.mail-archive.com/
wien at zeus.theochem.tuwien.ac.at/msg06932.html)  and have a queries:

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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