[Pw_forum] Clarification on how to compute elastic constants

[bamidele ibrahim]

 Dear all,
Please, i need some clarification on the following  issues on how to calculate elastic constants, 
1. When performing the calculation, is it correct to set 'calculation=scf' or 'relax'? For either of the two cases, can  anybody in the house give me an explanation on it.
2. since we need to set ibrav=0, and define explicitly the primitive vectors for any crystal we are dealing with then, is it necessary to define all the atoms in the primitive cell of the crystal explicitly?  for example ZnSe which has 8 atomic positions if ibrav=0 and this in the cubic B3 phase. 
3. Do i need to use cell dynamics or ion dynamics for the optimization of the cell?

I will be delighted if anybody can give me an explanation on this issue.

Thanks

 
Adetunji Bamidele Ibrahim(PhD Student)
Department of physics,University of Agriculture,
Abeokuta, Ogun State,Nigeria.
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