[Pw_forum] atomic positions

[Stefano de Gironcoli]

Dear Adebayo Abdulganiy
   there is no magic.
   what you need to know are the positions of all the atoms in your unit 
cell and the three fundamental lattice vectors that define the cell.
   If you do not have this information there is no way you can build the 
structure.
   Once you have it, the cell shape can be defined using the ibrav and 
celldm variables (see their definitions) or choosing ibrav=0 and 
explicitly giving the three vectors. The positions can be defined using 
carthesian coordinates (in bohr, angstrom or unit of celldm(1)) or 
crystal coordinates (that is as fractions of the three fundamental 
vectors defining the cell). Read the explanation given about the 
ATOMIC_POSITION card.

stefano

Abolore Musari wrote:
> Dear QE user
>  Pls I need to know how the atomic positions of the system used in the
> examples like Si, SiO2 e.t.c are gotten so that i can apply it for the
> material i would like to work on. In fact i would appreciate a detail
> explanation on this ccos I visited bilbao Crystallographic server and still
> couldnt get a clue on how to explore the website.
>
> thanks
>
> Adebayo Abdulganiy
> university of Ibadan
> Nigeria
>
>   
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