local relaxation

[asiyeh_shokri2]

Hello

I would like to know if it is possible to do local relaxation in a bulk matterial just around a defect? fixing other atoms? if selection dynamics in POSCAR is the way, then should I have also some tags in INCAR file for it?

Best regards,
Asiyeh

[pedro_melo]

Dear asiyeh_shokri2,

It is possible to perform geometry optimisation calculations where certain ions are fixed. Please see the entry for "Selective dynamics" on the table here wiki/index.php/POSCAR, where it explains how to specify which atoms you want fixed and which are to move inside the POSCAR file.

Kind regards,
Pedro

[asiyeh_shokri2]

Thank you so much I did calculation as it is in the link you send. I have also another question. Can I do the optimization in a restricted manner? Do not letting atoms to move out of a limited radius?

Best regards,
Asiyeh

[pedro_melo]

Dear Asiyeh,

I do not think that is possible at all. I can tell you that from my experience with calculations on systems with defects, while the lattice parameters are kept fixed, positions of individual atoms are allowed to change. I would advise you to check if the total energy changes, as this can influence your estimation of formation energies. This would be important when reporting how thermodynamically favourable your defect is.

Kind regards,
Pedro

[asiyeh_shokri2]

Thank you so much for your answer.

Best regards,
Asiyeh