[Pw_forum] bravais lattice of Cmca

[Sandro Scandolo]

Hi,

> I calculate the Cmca(#64) structure.
> But I wonder which ibrav number is.
> This structure is orthorhombic.

it's base-centered orthorhombic, ibrav=9.

> I could check the other program.
> It is C-center based orthorhombic.
> Also, I got the atomic position.
> But I didn't get a correct result.
>

Notice that QE assumes that the centering occurs on the ab basal plane. 
Moreover if using "crystal" for the atomic positions, QE assumes that 
positions are expressed in terms of the primitive cell, not in terms of 
the conventional (orthorhombic) cell.

Sandro


-- 
Sandro Scandolo -- http:/www.ictp.it/~scandolo