[Pw_forum] elastic properties

[Stefano de Gironcoli]

Dear kada galami,
  what you need to do is to calculate the stress for the equilibrium  
geometry and for a few slightly deformed cell shapes.
  The way you choose to describe each of these cells is up to you.
  Ibrav=0 is an option that gives you the possibility to define  
directly the lattice vectors (in unit of celldm(1)).

   If you want to describe a simple cubic cell of lattice spacing 3.14 bohrs
  it's up to you to define

   ibrav=1, celldm(1)=3.14

   or

   ibrav=0, celldm(1)=3.14
   CELL_PARAMETERS
     1.0 0.0 0.0
     0.0 1.0 0.0
     0.0 0.0 1.0

   or

   ibrav=0, celldm(1)=6.28
   CELL_PARAMETERS
     0.5 0.0 0.0
     0.0 0.5 0.0
     0.0 0.0 0.5

  hope this helps,

stefano

Quoting kada galami <physolde at yahoo.fr>:

> hi
>  dear evayz
> i spoke to you earlier in the forum about the elastic properties   
> with ibrav = 0 ( free lattice
> i have some questions :
>
> 1- we do the calculation of elastic propreties only with ibrav= 0
> 2- i read about the input ibrav= 0
> we have to put only the celldm(1)
> and the cell parameters
> where i can get the cell parameter, i think have somthing with basic vectors
>
> thank you in advance for your help
>
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> ---------------------------------------------------
> phd student
> departement de physique
> faculte de science
> universite de sidi bel abbes
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