Calculating migration energy using NEB

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Mahesh_chandran · #1 Post by **Mahesh_chandran** » Mon May 29, 2006 10:22 am

Hi,
I want to calculate the migration energy for an atom moving into the nearest vacant site in a solid. I also need to find the minimum energy path (MEP).

I tried using NEB with full structural relaxation of the images (ISIF=3). I find that it takes awfully long time for the convergence and the structure seems to be distorted significantly along the MEP.

Is it necessary to relax all the cell parameters to obtain correct MEP? Or can one fix the cell shape and volume (ISIF=2)? Which among the two will give the correct energy barrier for migration?

regards
MC

konglt · #2 Post by **konglt** » Mon May 29, 2006 12:19 pm

In my opinion, the cell shape and volume should not be changed during the NEB calculations. Because of the elastic forces, neither the force nor the stress tensor is ''real'' for the simulation cell; if you allow a fully structural relaxation, the resultant cell could not be correct.

Mahesh_chandran · #3 Post by **Mahesh_chandran** » Tue May 30, 2006 4:34 am

How does one account for the local structural distortion which would occur during the migration of an atom?

tjf · #4 Post by **tjf** » Tue May 30, 2006 9:04 am

[quote="Mahesh_chandran"]How does one account for the local structural distortion which would occur during the migration of an atom?[/quote]

Keep it local: use a bigger supercell!

tsemi · #5 Post by **tsemi** » Thu Jun 18, 2009 2:03 pm

Using the NEB method, how does one extract the migration energy from the output files?

Thank you,
torey