problem optimizing tio2 nanotubes

[zhySarah]

Hi,

I built two different (1 0 1) tio2 nanotubes (tnt) using tube wrapper, tnt(6,0) and tnt (8,0). After Optimizing using the same settings (see attachement 1), I got two different optimized structures (attachement 2&3, before optimization on the left and after optimization on the right). I am expecting structures like optimized tnt(6,0). Can anyone tell me why is something like opt tnt (8,0) happening?

Thanks

[Anders Blom]

I doubt that potential is good for TiO2, but you'll have to check the reference. Just because a potential supports nominally the included elements doesn't give any guarantee that it actually works for all possible combinations. Actually, this is a silicate potential that can be used with Ti impurities, if memory serves me right.

[zhySarah]

I doubt that potential is good for TiO2, but you'll have to check the reference. Just because a potential supports nominally the included elements doesn't give any guarantee that it actually works for all possible combinations. Actually, this is a silicate potential that can be used with Ti impurities, if memory serves me right.

Hei, Anders Blom!

Thanks for your answer. I understand that these built-in potential settings may not suitable for my case. So I now am thinking to use ATK-DFT calculator to set up for my structure, but am a little struggled with where to start. It would be great if you can give me some suggestions on a set of parameters I can begin with, for instance exchange correlation type and functional, mech cutoff, and max force and stress. Thanks in advance!

[Anders Blom]

I suggest starting with defaults except  for the k-point sampling in the Z direction which needs to be larger than default - try 9 or 13.

After that - or more preferably before - run several of the tutorials on our website and also check the general literature on electronic structure calculations to learn about these topics. It will not be possible for us to teach you all these concepts here on the Forum