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[Bousquet Eric <Eric.Bousquet@ulg.ac.be>]

Dear Santosh Bobade,

The space group of BaTiO3 in cubic paraelectric phase is 221 (Pm-3m), 
and the atomic positions in unit cell are:
                            Ba 0.0 0 0 0.0
                            Ti 0.5 0.5 0.5
                            O1 0.5 0.5 0.0
                            O2 0.5 0.0 0.5
                            O3 0.0 0.5 0.5
At least five positions are requiered to find the BaTiO3 structure!

Best Regards,
Eric Bousquet

santosh_bobade@yahoo.com wrote:
> Dear Abinit user
>
> I am trying to know more about code so that it can be really 
> exploited for. while doing this I am trying to run some response function
> calculation for BaTiO3 to find out whether I can match mine with reported value.  
> Here is detail what exactly the Problem is
>
> spgroup 123 
>                   
> Ba 0.0 0 0 0.0                    Ba 0.0 0 0 0.0
> Ti 0.5 0.5 0.5                    Ti 0.5 0.5 0.5
> O1 0.5 0.5 0.0                    O1 0.5 0.5 0.0
> O2 0.5 0.0 0.5                    O2 0.5 0.0 0.5
>                                   O3 0.0 0.5 0.5
>
> natom 4                            natom 5
> typat 1 2 3 3                      typat 1 2 3 3 3 
> ETOT -55.*****                    -68.******
> ecut 40
> kptopt 1                           kptopt 1
> nkpt 10                            nkpt 10
> kptrlen 45                         kptrlen 45
> In both cases lattice constants are same. and other inputs are also same.
> The difference is in first case I used spacegroup and in later atomic 
> cordinates
> are explicitely provided.
>
> Now what I found the Total Energy is different although the case in which 
> coordinates were input, predicts same space group ie 123.
>
> The only thing that bothers me the energy difference  
> i used a=b=3.98, c=4.03 and ecut =40 for both run
> can anybody throw light on this aspect?
>
> Now I think, This will make my case.
> Thank for reply.
>
> With Regards
> Santosh Bobade