[Wien] Volume optimization for a hexagonal structure

[Ushma Ahuja]

Dear Wien2k community,

I have been trying to volume-optimize a hexagonal structure (MoTe0.5S1.5).
I first used the option 1 (energy vs. vol. with constant parameter ratio) and then headed on to option 2 (energy vs. c/a with constant volume) and obtained the minimum energy curve also.
I then used the c/a for minimum energy from this curve and derived the lattice parameters a and c using the volume formula for a hexagonal structure.
But I observed that these values of a and c differ from those updated in the case.struct file after the completion of option 2.
Which values of a and c should I proceed with now? The one I obtained from the minimum energy curve+volume formula or the one updated in the case.struct file.
(For once I created a new structure file with the lattice parameters obtained from the optimization calculations. But this structure also gave me a Fermi error!)
Kindly guide.

regards,

Ushma Ahuja
Faculty of Engineering
Mohan Lal Sukhadia University
Udaipur
India