[CPMD-list] Problems optimizing monoclinic unit cell

[Ewald Pauwels]

Dear Axel,

First of all I would to thank you for your swift response.

>this is to be expected. if you use CELL VECTORS, cpmd does not even 
>try to detect cell symmetry and thus assumes a triclinic cell (and
>cannot take advantage of the symmetry).
>
>  
>
In retrospect, this is indeed quite logical. So, whatever the original 
symmetry, using CELL VECTORS would result in a "triclinic" cell in the 
CPMD output?

>as far as i understand it - please correct me anybody, if i am mistaken,
>i'd really like to be certain about this - you have give the cell dimensions 
>for the _conventional_ cell (but only the atom positions for the primitive cell). 
>i know at least one more code, that uses the exact same conventions, so 
>i am pretty sure, that this is intentionally so.
>  
>
Actually, I have given the cell dimensions for the _primitive_ unit cell 
(which is monoclinic). This cell contains four glycine molecules, for 
which I have specified all atom positions explicitly. So, I might have 
misunderstood, but I don't think I have used a conventional cell in any way.

Sincerely,
Ewald.



-- 
Ewald Pauwels
Centre for Molecular Modelling
Laboratory of Theoretical Physics
Ghent University
Proeftuinstraat 86
B-9000 Gent
Belgium
ewald.pauwels at UGent.be
+32 9 264 65 76