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[hamed saidaoui <hamed.saidaoui@gmail.com>]

2009/2/24, Anglade Pierre-Matthieu <anglade@gmail.com>:

Hi,

If I understand clearly the phase transition you seek is just changing
the angles of your  rhomboedral structure ?
In this case you could start by computing the equation of state (E(V),
  E(a), E(P) ...) of both phases.
This will help you decide on the relative stability of both phases and
also help locating the
pressure at which  the phase transition may occur.
Afterwards You'll have to findout the phase transition process. In a
best case it could simply happens spontaneously under high pressure
and cell optimization.  In a worst case it could be out of reach of
DFT (for instance in case your phase transition is related to a fine
electronic exchange effect).

regards

PMA


On Tue, Feb 24, 2009 at 3:41 PM, walid firas <firas.walid@gmail.com> wrote:
> dear users , hello
> i m trying to determine the transition pressure , but i don't know how to do
> that with abinit
> itried to vary the rprim but no phase transition was detected until now ,the
> phase transition is from a rhombohedral to rhombohedral structure which
> differs by angle
> i want to know if there is a method which allow me to detect the phase
> transition without testing a lot of structures arbitrarily
> regards
>




--

Pierre-Matthieu Anglade

thank you for your ananswerswer 

but the problem is that i have to try a lot of angles to reach the phase transition ,with the optimization of structure at every angle  the task looks painfull so i want to know how to choose or predict the structure which give the phase transition without testing an enormous number of structures