[Pw_forum] EOS for Tetragonal Systems

[Ezad Shojaee]

Thank You Eyvaz
for EOS in Tetragonal Systems, it was mentioned in the archive:
 
You have to optimize first c/a keeping the volume fixed ... Once you have E(V), you can fit it to an equation of state, much in the same way you would for a cubic system.
 
imagine we have optimized c/a for a range of volumes in a Tetragonal lattice. The program ev.x whice fits the data to an equation of state, asks to specify the lattice. Does the sentence "much in the same way you would for a cubic system" means that we should provide (a   E_tot) as an input (ofcourse 'a' is according to the optimized c/a for each volume) and treat the Tetragonal like a Sc? or we should provide (V    E_tot) as we do for Hexagonal systems and treat it like a Hexa? If it is the first, so we should treat BCT's like a BCC? maybe wrong, but i have much more reasonable results in the second way(treating like a Hexa)!
Thanx again
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