Force is not going below 0.1 eV/Å in my NEB calculation

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riyazpu
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Joined: Mon Oct 10, 2022 6:24 am

Force is not going below 0.1 eV/Å in my NEB calculation

Post by riyazpu »

Dear All
I am doing an NEB calculation for N-O dissociation barrier on a metal surface. First, I used IBRION = 3, IOPT=3, POTIM = 0 and TIMESTEP = 0.03, and force converging until 0.1 eV/Å and not going down. Then I increased the TIMESTEP to 0.1 and restarted the calculation but the force is not converging. I also changed IOPT to 2nd order optimizer IOPT= 1 and 2 but still, the force is not stabilizing. Can anyone suggest a solution to the problem? As I already stated, I tried different solutions provided in this forum but had no luck.
I have attached the input I used.

Thank you

Best
Riyaz
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graeme
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Re: Force is not going below 0.1 eV/Å in my NEB calculation

Post by graeme »

I don't see any OUTCARs - I need them to see what is going on.
riyazpu
Posts: 7
Joined: Mon Oct 10, 2022 6:24 am

Re: Force is not going below 0.1 eV/Å in my NEB calculation

Post by riyazpu »

graeme wrote:
> I don't see any OUTCARs - I need them to see what is going on.
Thank you for your response, I have attached the folder with OUTCARs, please have a look.

Thank you for your time.
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graeme
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Re: Force is not going below 0.1 eV/Å in my NEB calculation

Post by graeme »

It's converging - you just have a small timestep of 0.03. You can up to a value of 0.1 and continue the calculation.
riyazpu
Posts: 7
Joined: Mon Oct 10, 2022 6:24 am

Re: Force is not going below 0.1 eV/Å in my NEB calculation

Post by riyazpu »

graeme wrote:
> It's converging - you just have a small timestep of 0.03. You can up to a
> value of 0.1 and continue the calculation.
Though I tried timestep 0.1 and the force started to destabilize. But yes I will try again. Another question is, should I rather try a dimer calculation, when the force reaches around 0.1 eV/Ang with CL-NEB or continue with CL-NEB and converge the force?

Thank you
graeme
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Re: Force is not going below 0.1 eV/Å in my NEB calculation

Post by graeme »

just get this to converge before you try anything more fancy. And check that you have the same settings in your NEB as compared to the endpoints - I see a disconcerting shift in the entire top layer between the neb images and the final structure.
riyazpu
Posts: 7
Joined: Mon Oct 10, 2022 6:24 am

Re: Force is not going below 0.1 eV/Å in my NEB calculation

Post by riyazpu »

graeme wrote:
> just get this to converge before you try anything more fancy. And check
> that you have the same settings in your NEB as compared to the endpoints -
> I see a disconcerting shift in the entire top layer between the neb images
> and the final structure.
Ok..Thanks for the tips and yes I also see a bit of a shift in the surface atoms during optimization.
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