[Pw_forum] crystal coordinates and ibrav=12

[Paolo Giannozzi]

On Wednesday 07 December 2005 12:29, Andrea Vittadini wrote:

> anybody tried to run PWSCF calculations on a Monoclinic cell
> (ibrav=12) with "crystal" coordinates?

I didn't!

> I used two coordinates sets, both with the following cell parameters:
> celldm(1)=   7.154503  celldm(2)=   2.759416  celldm(3)=   1.000000
> celldm(4)=   0.362396
>
> As far as I can see, sets 1&2 should be (approximately) equivalent, yet
> set #1 gives strange results.

the code prints both the crystal axis and the cartesian atomic coordinates 
in 2pi/a units (if it doesn't, try "verbosity='high'"). From such data you
should be able to find out what is happening. This is what the axis for
the monoclinic P, i.e. ibrav=12, should look like:
  =============================
     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, 
  celldm(1)=a, celldm(2)=b/a, celldm(3)=c/a, celldm(4)=cos(ab)

(see file Doc/INPUT_PW towards the end)

Paolo
-- 
Paolo Giannozzi             e-mail:  giannozz at nest.sns.it
Scuola Normale Superiore    Phone:   +39/050-509876, Fax:-563513 
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