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!

## Atomic structure relaxation [SOLVED]

### Re: Atomic structure relaxation

Dear cgs12

see input variables opcell and ionmove ...

best wishes

Nawzad

see input variables opcell and ionmove ...

best wishes

Nawzad

### Re: Atomic structure relaxation

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!

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

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]

Hi,

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

Cheers

Boris

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

Cheers

Boris

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Boris Dorado

Atomic Energy Commission

France

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Boris Dorado

Atomic Energy Commission

France

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