[Pw_forum] Quick question on coordinates
Paolo Giannozzi
giannozz at nest.sns.it
Wed Feb 27 16:09:03 CET 2008
Miguel Martinez wrote:
> monoclinic (p)
> =============================
> a1 = (a,0,0), a2= (b*sin(gamma), b*cos(gamma), 0), a3 = (0, 0, c)
> where gamma is the angle between axis a and b
>
> base centered monoclinic
> =============================
> a1 = ( a/2, 0, -c/2),
> a2 = (b*cos(gamma), b*sin(gamma), 0),
> a3 = ( a/2, 0, c/2),
>
> ¿Is it right? ¿Is it a typo?
what is right and what is a typo? As far as I know, the documentation
exactly reflects what the code does (see flib/latgen.f90) :
else if (ibrav == 12) then
sen=sqrt(1.d0-celldm(4)**2)
a1(1)=celldm(1)
a2(1)=celldm(1)*celldm(2)*celldm(4)
a2(2)=celldm(1)*celldm(2)*sen
a3(3)=celldm(1)*celldm(3)
else if (ibrav == 13) then
sen = sqrt( 1.d0 - celldm(4) ** 2 )
a1(1) = 0.5d0 * celldm(1)
a1(3) =-a1(1) * celldm(3)
a2(1) = celldm(1) * celldm(2) * celldm(4)
a2(2) = celldm(1) * celldm(2) * sen
a3(1) = a1(1)
a3(3) =-a1(3)
The case ibrav=13 has been corrected more than once by the way.
If you have evidence that there is something wrong above, please
explain what exactly and why
Paolo
--
Paolo Giannozzi, Democritos and University of Udine, Italy
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