Migration barrier unexpected too large

Vasp transition state theory tools

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gitosr
Posts: 5
Joined: Fri Mar 25, 2022 5:51 pm

Migration barrier unexpected too large

Post by gitosr »

Dear Henkelman,

I am studying the compound Cu4TiTe4 in a 2x2x1 supercell that contains 36 atoms. One of the Cu atoms has a partial occupation of 1/4, and I would like to calculate the migration from one of those positions to another within the same 'subcell'. However, when calculating the migration, I obtain a value of around 4.5 eV, whereas I would expect a much lower value. Additionally, the images do not converge, and I don't understand why. I am attaching the calculations in case you could help me. Thank you in advance.

Best regards.
Jorge
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migration_cutite.tar
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graeme
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Re: Migration barrier unexpected too large

Post by graeme »

The problem is that you have not linked our vtstcode into your vasp binary. So what is happening is that you have turned off vasp optimization with IBRION=3, POTIM=0 but then don't have the vtst code to do the optimization with your IOPT tag. So the reason that the barrier is so high is because it is just the barrier of the unrelaxed initial path.
gitosr
Posts: 5
Joined: Fri Mar 25, 2022 5:51 pm

Re: Migration barrier unexpected too large

Post by gitosr »

Thank you very much, Professor Henkelman. I repeated the migration with the correct executable and it seems to have worked perfectly. The current barrier values are nearly 10 times smaller, which makes much more sense. I apologise for any inconvenience.
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plot_C_to_A.jpg
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