UT theoretical chemistry code forum

Dear all,

In some VASP online examples (www.nsc.liu.se/lcsc2005/vasp/handson_excercises_4.ps), people have used the INCAR tag "IBRION=2" for their NEB computations. From this forum it is clear that one should IBRION=3 to reach convergence in the NEB computations.

Question. For the initial and final configurations of a given system is it reasonable to first optimize the atomic positions using the IBRION = 2 tag, and then, run the NEB (or CI-NEB) using IBRION=3?

I tried IBRION=2 for the OPT and NEB runs, but the NEB computations don't converge in a reasonable period of time. Then I tried IBRION=3, but the optimization job did not converge. The only way that the system reached converge in both the optimization run and the NEB run was by using IBRION=2 for the optimization and IBRION=3 for the NEB. Is this OK? Or should one try to converge both the NEB and optimization runs using IBRION=3?

thanks,

It's definitely OK. Any IBRION is OK if it can be converged.

Dear all,

Perhaps, I did not explain well myself. I understand that as long as the NEB convergence is achieved, it does not matter if one uses IBRION=2 or IBRION=3.

But my question is, can one optimize the initial and final configurations of an NEB-calculation using IBRION=2; and then run a proper NEB-job using the IBRION=3 optimizer?

Thanks,

yes (and please do not cross-post on the vasp forum!)