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Atomic structure relaxation

Posted: Fri Nov 02, 2018 8:47 pm
by cgs12
Hi,

I would like to ask if it is possible to perform full atomic position relaxation in Abinit. More specifically what I mean by this is that I do not have information on the space group of crystal structure in mind and wish to allow all atomic positions to relax fully so that the result converges to a particular space group corresponding to the minimum total energy at ground state. However, Abinit seems to perform relaxation based on the symmetry groups imposed in the starting structure, i.e. I am not able to start from a random space group and hope that the end result gives the correct space group.

Is it also possible to perform structure relaxation by fixing two lattice parameters and allowing the third lattice parameter to relax to minimize energy?

Thanks so much for your kind attention!

Re: Atomic structure relaxation

Posted: Mon Nov 05, 2018 11:32 am
by new_986
Dear cgs12
see input variables opcell and ionmove ...
best wishes

Nawzad

Re: Atomic structure relaxation

Posted: Mon Nov 05, 2018 4:51 pm
by cgs12
Dear Nawzad,

Thanks so much for your reply. What I meant was something similar to having optcell=2. However, optcell=2 allows for full relaxation subject to symmetry imposed in the initial guess structure. Here I do not know the symmetry groups of the materials of interest and wish to find those out through minimizing energy in DFT. Therefore full relaxation without symmetry imposed would be ideal.

Does it make sense for me to try perturbing all the atomic positions so that there is very minimal symmetry and nearly-full relaxation of nuclear positions can be done? Or must I resort to identifying all the potential space groups of the material of interest through experiments, other computational studies etc, and then perform DFT calculations accordingly?

Thanks!

Re: Atomic structure relaxation

Posted: Fri Nov 09, 2018 8:59 pm
by new_986
cgs12 wrote:Dear Nawzad,

Thanks so much for your reply. What I meant was something similar to having optcell=2. However, optcell=2 allows for full relaxation subject to symmetry imposed in the initial guess structure. Here I do not know the symmetry groups of the materials of interest and wish to find those out through minimizing energy in DFT. Therefore full relaxation without symmetry imposed would be ideal.

Does it make sense for me to try perturbing all the atomic positions so that there is very minimal symmetry and nearly-full relaxation of nuclear positions can be done? Or must I resort to identifying all the potential space groups of the material of interest through experiments, other computational studies etc, and then perform DFT calculations accordingly?

Thanks!


Dear cgs12
give nsym input variable 0, it will give you number of symmetries and space group automatically...

beast regards
Nawzad

Re: Atomic structure relaxation  [SOLVED]

Posted: Mon Nov 12, 2018 1:02 pm
by Boris
Hi,

If you want to remove all symmetry constraints in your calculation, just set nsym to 1.

Cheers
Boris