[Pw_forum] Calculation of orthorhombic lattice parameters from the basis vecotrs

[Éric Germaneau]

Dear Kondal,

The first line of the matrix correspond to *a*, the second to *b*, and 
the third to *c*.
In order to get a, b, and c, just calculate the norm of the 
corresponding vectors.
Don't forget to  multiply by alat to have them in Bohr.
Then, /alpha/ is the angle between vectors *b* and *c*, so you just need 
to calculate the dot product *b.c*.
You'll get /alpha/ by doing

    /alpha/ = acos( *b.c* / b*c )

Finally, just do the same thing for /beta/, the angle between *a* and 
*c*, and /gamma/, the angle between *a* and *b*.

Hope it helps,

                            Éric.

On 12/27/2011 01:05 AM, yedu kondalu wrote:
> Dear users,
>
>      I did the structural optimization of a compound belongs to the 
> space group /*Ibam**-72*/ (body centred orthorhombic) using variable 
> cell  (vc-relax) method.
>
>      lattice parameter (alat)  =      10.5862  a.u.
>      unit-cell volume             =     675.9126 (a.u.)^3
>
> The initial basis vectors
>                a(1) = (   0.500000   0.529989   0.537487 )
>                a(2) = (  -0.500000   0.529989   0.537487 )
>                a(3) = (  -0.500000  -0.529989   0.537487 )
>
> After the structural optimization the vectors are
>
>   new unit-cell volume =    614.83507 a.u.^3 (    91.10916 Ang^3 )
>
>   CELL_PARAMETERS (alat= 10.58624499)
>    0.529016060   0.479936985   0.510293152
>   -0.529016060   0.479936985   0.510293152
>   -0.529016060  -0.479936985   0.510293152
>
> 1.  How to calculate the lattice parameters  for this case ?
>
> 2. How to do the same for all the non cubic systems ?
>
> Can some body please explain me any method or reference books to do 
> the same ?
>
>
> Thanking you
>
> Regards
> KONDAL
>
>
>
>
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-- 
/Be the change you wish to see in the world
/ --- Mahatma Gandhi ---

Dr. Éric Germaneau 
<http://www.linkedin.com/pub/%C3%A9ric-germaneau/30/931/986>

Graduate University of Chinese Academy of Sciences
College of Physical Sciences
Yuquan Road 19A
Beijing 100049
China

/Please, if possible, don't send me MS Word or PowerPoint attachments
Why? See: http://www.gnu.org/philosophy/no-word-attachments.html/

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