[Pw_forum] alat and cell parameter

[Paolo Giannozzi]

The definition of "alat" is arbitrary. Typically it is
the lattice parameter, but it may be whatever. In vc-relax
calculations alat is kept fixed to the starting value, 
IIRC, while basis vectors are updated.

P.

On Fri, 2013-05-17 at 08:01 -0500, Dongsheng Zhang wrote:
> Good morning everyone,
> 
> 
> I tried to optimize a crystal structure by vc_relax, and found the
> cell parameter kept changing until it is optimum. However, the value
> of alat is always the same as the initial value. I think the alat
> value should be linear with the cell parameter since the system is a
> crystal.  What is the relationship between alat and cell parameter?
> Thank you for your help,
> 
> 
> Dongsheng
> 
> 
> 
> _______________________________________________
> Pw_forum mailing list
> Pw_forum at pwscf.org
> http://pwscf.org/mailman/listinfo/pw_forum

-- 
 Paolo Giannozzi, Dept. Chemistry&Physics&Environment, 
 Univ. Udine, via delle Scienze 208, 33100 Udine, Italy
 Phone +39-0432-558216, fax +39-0432-558222