Error while optimizing a structure

[medeepak]

Hi

I tried to optimize a structure of ZGNR with some structural defects , it becomes a haphazard structure within first few run only and continues to deteriorate . please someone tell what is wrong with my structure. I followed the procedure given in tutorials for optimization

regards
deepak

[medeepak]

for some reason i am not able to upload my files
it says "upload folder full"

[Anders Blom]

Try again, I just added 10 MB of space for attachments. Thanks for pointing it out!

[medeepak]

Hi

i am trying the following structure(in the script) to optimize a structure in 2008.10 version
the run goes on for the whole 100 steps as in the parameters and quits saying maximum no of steps reached

please tell me what am i missing
i included Total Energy and Forces parameters
but i dont know what else have left out

[Anders Blom]

One should never use the SingleZeta basis set for any real work, it's just for testing. Moreover, are you sure it is suitable to treat this is a molecule? The edges in Z are not hydrogen-terminated, and thus there will be dangling bonds which shift the Fermi level.

If you had ATK 11.2 you could relax this system in 10 seconds, using the Brenner potential

[medeepak]

Hi

this is just to check
now am in a different place where 11.2 version is there
is there any way to do it??

[medeepak]

hi

is there no way to optimize it here??

and also please tell/ give any link that uses the brenner potential to optimize in 11.2 version
i usually use the optimize block along with ATK-DFT which sometimes takes more than 3 days to optimize some structures

[Anders Blom]

There is such an example in the basic ATK tutorial, http://quantumwise.com/documents/manuals/latest/VNLTutorial/index.html/chap.gnr.html

[medeepak]

hi

thanks for the link
is there any other way to optimize the structure in 2008.10 version itself as it may take me a few days to go the place where 11.2 version is there

or please point out the mistake in the script i attached

regards
deepak

[Anders Blom]

As I wrote above, I don't think it's appropriate to relax the structure as a molecule, and the lack of terminating hydrogen atoms in Z will shift the Fermi level which can cause convergence problems. So I think in 2008.10 you can still get it to work if you put the system in a suitable unit cell and relax it as bulk, with periodic boundary conditions in Z.

In general, however, relaxations with DFT work better in 11.2 because we improved the algorithm and the accuracy of the forces.