[Pw_forum] monoclinic cell definition question

[Lorenzo Paulatto]

In data 13 maggio 2009 alle ore 16:38:29, Jonas Baltrusaitis  
<jasius_1 at yahoo.com> ha scritto:

>
> Fair enough. Big question is: a unique angle ab in monoclinic system if  
> transferred from cif file is 90o, e.g. not unique at all. one of the two  
> remaining angles is unique. hence I am trying to rotate the cell so this  
> unique angle comes into place, e.g. between a and b, as defined in pwscf  
> manual. it the get's complicated if x,y,z, coords should get rotated as  
> well

Exactly, that's why I was suggesting you to express the coordinates in  
crystal units, so you can do a simple premutation instead of a rotation.  
What *I think* you can do, to solve the problem in a formal way is:
1. write the cell basis vectors as provided by the cif file (C)
2. write the cell basis vectors as used by pw.x (P) using the same units  
of measure
4. compute R=P.C^-1
5. apply R to all the atomic coordinates from the CIF (intended as column  
vectors) file to get the coordinates for pw.x

Yet, I am more and more convinced that defining the cell axis by hand  
would be much simpler in this case.

regards

-- 
Lorenzo Paulatto
SISSA  &  DEMOCRITOS (Trieste)
phone: +39 040 3787 511
skype: paulatz
www:   http://people.sissa.it/~paulatto/

     *** save italian brains ***
  http://saveitalianbrains.wordpress.com/