Vasp transition state theory tools
6 posts • Page 1 of 1
I just want to make sure: is it a problem if NEB pathways go across unit cell boundaries? I have a unit cell setup where I cannot avoid going across a boundary/along the unit cell edge. In the VASP forum it was mentioned by the head admin that this could lead to a pathological path, but I have never seen anything strange with it and I cannot see why it should be a problem either with PBCs. I would be interesting in hearing other experiences.
Our NEB implementation should be airtight in regards to that aspect. I have never had any problems with it, but I guess anything is possible. But I usually try to set up the calculations in such a way that any boundary crossing is unlikely. So if you witness any funny business with our implementation then please report it asap, it would be much appreciated.
I usually try to set up my unit cells up, too, so that no boundary crossing takes place. But I was trying a number of different things and ended up with this pathway. So far, everything looks normal and I have not observed any funny things, e.g. discontinuities, when the adsorbate crosses the cell boundary. Also I have checked the TS I found by vibrational analysis. Thus, so far things seem to work fine with cell crossing but of course I will let you know, should I enounter anything strange. Thanks!
Just to check back in, I actually performed a test on one of my diffusion pathways. I took the converged pathway which crosses a unit cell boundary and changed the unit cell such that it (as much as possible) stays within that cell. No energy and force changes apart from noise (energy changes <0.001eV and forces <0.01eV/A) so it seems indeed to be airtight. I thought you would like to know.