ABINIT Discussion Forums

Hi abiniters,

I would like to substitute one oxygene atom among 2 types of oxygene by another atom (one in octahedral site and the other one in tetragonal site) in a cell contaning 10 oxygenes and other atomes.
So, how can I define the symmetry in this case?
Then, do you think it is ok if i make only the relaxation and not a full optimization?

Dear ziedhosni,

this is what I think. Maybe others will have better answers.

Regarding the symmetry; if you know specifically which symmetry your substitute cell obtains, you can fix it using the 'spgroup' variable. On the other hand, if you don't, you could leave out the rprim and spgroup from the input file and let abinit determine the symmetry by itself.

Regarding the optimization. I think that it depends on a few facts:
1] What kind of atoms are your substitution atoms. If they are very 'similar' to oxygen, maybe you don't have to carry on the full relaxation, because the electronic environment won't change much.
2] How big is you unit cell. If its very big, then the change of the electronic configuration won't have much influence on the far away atoms, and the cell dimensions won't change much itself.

Cheers!

Igor L.

hi,
I want to substitute one Ca by one La then 2 Ca by two La ..( I have 10 Ca in the system).
I use
acell 9.430723 9.430723 6.917214 angstrom

My system contain 42 atoms and among the 10 Calcium there are 6 that are octahedral and 4 tetrahedral.

I'm sorry, these were not questions for you, but only statements. Maybe some of the more experienced folk could answer that. On the other hand, you can always test it.

Igor