The ABINIT Users Mailing List ( CLOSED )

[Anglade Pierre-Matthieu <anglade@gmail.com>]

Hi,

Did you tried a cell optimization at a pressure high enough to be sure
that the phase transition should happen ?
And what about running a damped molecular dynamic with fixed stress ?

regards

PMA

PS: in case you try one of this options don't forget to deal with
"nsym" and ist effects.

On Tue, Feb 24, 2009 at 5:02 PM, hamed saidaoui
<hamed.saidaoui@gmail.com> wrote:
>
>
> 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
>
>



-- 
Pierre-Matthieu Anglade