[Pw_forum] input structure for ibrav=9

[Amin Torabi]

Dear Paolo,
I did exactly the same thing, but I expect to see all the angles to be 90,
while Xcrysden does not exhibit this.
How come V1 and V2 are not orthogonal?
And do I have to express the fractional atomic position in terms of A,B,C
or V1, V2 and V3?
Amin

On Mon, Nov 28, 2011 at 3:38 AM, Paolo Giannozzi <giannozz at democritos.it>wrote:

>
> On Nov 28, 2011, at 6:12 , Amin Torabi wrote:
>
> > I have some problem in introducing a base-centered orthorhombic
> > structure (ibrav=9) to QE.
> >
> > I have entered the cell parameters in A, B, C, cosAB, cosBC, cosAC
>
> you need only A, B, C (in Angstrom); cosAB, cosBC, cosAB are ignored.
> Or: celldm(1)=a (in Bohr), celldm(2)=b/a, celldm(3)=c/a (celldm(4:6)
> ignored).
>
> This is what you will get for the three unit translations v1, v2, v3
>                 9          Orthorhombic base-centered(bco) celldm(2)
> =b/a
>                                                            celldm(3)
> =c/a
>                     v1 = (a/2, b/2,0),  v2 = (-a/2,b/2,0),  v3 =
> (0,0,c)
>
> In the development version of QE, also ibrav=-9 is present:
>                -9          as 9, alternate description
>                     v1 = (a/2,-b/2,0),  v2 = (a/2,-b/2,0),  v3 =
> (0,0,c)
>
> P.
> ---
> Paolo Giannozzi, Dept of Chemistry&Physics&Environment,
> Univ. Udine, via delle Scienze 208, 33100 Udine, Italy
> Phone +39-0432-558216, fax +39-0432-558222
>
>
>
>
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-- 
Amin Torabi
Ph.D. Student
Chemistry Department
The University *of* Western Ontario
London, On Canada, N6A 5B7
Phone: 519-661-2111 Ext: 87871
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