UT theoretical chemistry code forum

Dear all,

I am using the NEB method to calculate diffusion energy barrier of octahedral interstitial oxygen in tungsten bulk mater. The initial and final sites of oxygen are two neighbor octahedral interstice. The problem is that the dimension of the cell along x, y and z changed when the O diffusion from initial state to final state. How to deal with this situation? Please give some advice. Thanks!

If the octahedral sites are equivalent, it is a little surprising that the cell shape is changing.

But anyway, as long as the cell changes are small, you can calculate your band keeping the cell relaxed. Just make sure that you re-run the calculation after it converges so that the effective plane wave set is the same for each image. You will also generally need more accurate parameters (e.g. cutoff and k-point grid) to compare the energies of cells with a different shape.

We are close to releasing a solid-state version of the NEB which can deal with significant cell and atomic motion in the same reaction pathway. We'll post a note when it is available.