[Q-e-developers] ibrav = +/- 9

[Paolo Giannozzi]

So do I. I just corrected it. Paolo

On Fri, Nov 6, 2015 at 4:38 PM, stefano de gironcoli <degironc at sissa.it>
wrote:

> On 06/11/2015 16:21, Lorenzo Paulatto wrote:
> > Dear All,
> > there is a small bug or a problem with the documentation of ibrav= -9
> >
> >
> > The Doc says:
> >
> > 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)
> > -9          as 9, alternate description
> >      v1 = (a/2,-b/2,0),  v2 = (a/2,-b/2,0),  v3 = (0,0,c)
> v1 = v2 ?
> i think the code is right and the doc is wrong... or both are wrong :-)
> stefano
> >
> > However the code says:
> >
> >       IF ( ibrav == 9 ) THEN
> >          !   old PWscf description
> >          a1(1) = 0.5d0 * celldm(1)
> >          a1(2) = a1(1) * celldm(2)
> >          a2(1) = - a1(1)
> >          a2(2) = a1(2)
> >       ELSE
> >          !   alternate description
> >          a1(1) = 0.5d0 * celldm(1)
> >          a1(2) =-a1(1) * celldm(2)
> >          a2(1) = a1(1)
> >          a2(2) =-a1(2)
> >       END IF
> >
> > Which means:
> > -9          as 9, alternate description
> >      v1 = (a/2,-b/2,0),  v2 = (a/2,b/2,0),  v3 = (0,0,c)
> >
> >
> > I.e the sign of the y-component of v2 is the opposite.
> >
> > I'm writing here because I do not know which of the two is correct.
> Thanks to
> > G Radtke for bringing this to my attention (He thinks that the Doc is
> correct
> > and the code is wrong)
> >
> > LP
> >
> >
>
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-- 
Paolo Giannozzi, Dept. Chemistry&Physics&Environment,
Univ. Udine, via delle Scienze 208, 33100 Udine, Italy
Phone +39-0432-558216, fax +39-0432-558222
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