[Pw_forum] Body Centered Tetragonal

[vtmtrinh at caltech.edu]

Hi Eyvarz,


Thanks for your message.
Yes, I did this way before.  However, when I checked the output, the
crystal axes (cart. coord. in units of a_0) are still the same ones as
defined in the input_PW, i.e:

V1 = a/2(1,-1,c/a), V2=a/2(1,1,c/a), V3=a/2(-1,-1,c/a)

If use these vectors to duplicate the structure e.g in z-direction (make
supercell to see how it looks like), the duplicated structure lie in wrong
direction (as I doubted).  This makes sense since the original structure
has the crystal axes as:

p1=(a,0,0), p2=(0,a,0), and p3=(a/2, a/2, c/2).

I think another way to have the consistency is to project the original
structure to the crystal axes used in QE .  Then use the resulting
structure for the input_PW. (I thought by simply changing the primitive
vectors in the code would be faster if I knew where it is  :-)).  Let me
try this way and see how it goes.

Best,

Trinh






> Hi,
>
> --- On Wed, 1/27/10, vtmtrinh at caltech.edu <vtmtrinh at caltech.edu> wrote:
>
>> Therefore, I cannot use the current coordinates that I have
>> for the input to run pw.x.
>
> You can use "angstrom" keyword in Atomic_Positions if you have them in
> Cartesian and Angstrom, or "alat" - again, Cartesian, but wrt the lattice
> parameter a_0.
>
> Bests,
> Eyvaz.
>
> -------------------------------------------------------------------
> Prof. Eyvaz Isaev,
> Theoretical Physics Department, Moscow State Institute of Steel & Alloys,
> Russia,
> Department of Physics, Chemistry, and Biology (IFM), Linkoping University,
> Sweden
> Condensed Matter Theory Group, Uppsala University, Sweden
> Eyvaz.Isaev at fysik.uu.se, isaev at ifm.liu.se, eyvaz_isaev at yahoo.com
>
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