UT theoretical chemistry code forum

Hi!

I have a question about EDIFF and EDIFFG for VASP setting.

I actually used following setting for my calculations.

System: LaFeO3

EDIFF: 1E-07
EDIFFG: -0.0005

These were OK but for surface calculations, I can not have convergence with these setting.

How you all set EDIFF and EDIFFG for your surface calculations?

Another question is I try to see what will be the optimum no. of layer for my system. 5L is OK. But If I extend my system as 7L and 9L, no convergence. I try to add dipole correction as my system has tilted octahedrals and I can not have "exact" symmetry even though I have identical surface termination.

Please share your ideas and experince.

Thanks,

Chan-Woo

These questions are probably more appropriate for the general vasp forum because they are not specific to finding transition state.
See: http://cms.mpi.univie.ac.at/vasp-forum/forum.php

Anyways, your ediffg is very low. A strict force criteria is -0.001, and many people would use -0.01 or higher. If you look at the change in the energy as you go from a force of 0.01 eV/Ang to 0.001 eV/Ang, it is usually negligible.

Your results should be converged with respect to the number of layers. If you are interested in a barrier, start with a few layers, then add subsequent layers until the barrier stops changing.

I don't have any experience with your system. Try the general vasp forum to see if others have more specific advice.

Actually, my final goal is to see how oxygen molecules dissociate on surfaces and how oxygen adatom will diffuse into the surfaces...... That is why I believed that this is the place. I thought that I need to know how other people who use NEB, Dimer methods, etc set their EDIFF and EDIFFG for thier research.

Anyway, as you said, there is noting about transition state. :) Sorry about that.

Your advice and explanation is truly helpful.

I appreciate your help.

Chan-Woo