[Pw_forum] murnaghan : bct

[Kucukbenli Emine]

Dear Sakhrawl

Equation of state is energy as a function of volume.
Therefore the crucial information needed in the ev.x program is volume, not lattice parameters.
The ev.x asks structure input to be able to calculate the volume from supplied lattice parameters.
For example, ibrav=2, celldm(1)=a for an fcc, you input the ev.x with "a vs Energy" data, it calculates volume=a^3*1/4 for each data point you have supplied and creates a "volume vs Energy" information instead, and then uses this to fit the EOS..
If you input "a vs Energy" for a simple cubic instead, it would calculate volume as a^3.
So, in principle, it is there to make things easier for the user..

Just use "hexagonal" and input the volume instead. (*<http://www.timeshighereducation.co.uk/418217.article>)

emine kucukbenli, postdoc at theos, epfl, switzerland
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.quantum-espresso.org/pipermail/users/attachments/20130428/79b2363d/attachment.html>