the structure does not converge

Vasp transition state theory tools

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weiyidan
Posts: 52
Joined: Thu Mar 02, 2017 8:01 am

the structure does not converge

Post by weiyidan »

Hi professor,
I prepare to do a calculation than a atom moves in the surface between the two bulk.

First, i use Ediff=1e-2, Ediffg=-0.3, IBRION=2, it works well.
Second, i use Ediff=1e-5, Ediffg =-0.05, IBRION=2, it works well too.
Third, i use Ediff=1e-5, Ediffg =-0.01, IBRION=1, the problem appears.

when I relax the heterojunction with parameters in the third step, it seems hard to converge. What is the problem? Can you give me some advice?
My calculation history is in the attachment.

Thanks for your attention.
Yidan WEi
Attachments
relax.rar
(5.51 MiB) Downloaded 556 times
graeme
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Re: the structure does not converge

Post by graeme »

Try lowering POTIM; a value of 0.3 is pretty large for IBRION=1.
weiyidan
Posts: 52
Joined: Thu Mar 02, 2017 8:01 am

Re: the structure does not converge

Post by weiyidan »

how about POTIM=0.15?
graeme
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Re: the structure does not converge

Post by graeme »

I typically use 0.1, but it really depends upon the stiffest mode in your system. You can try a few values to see when the convergence stabilizes.
weiyidan
Posts: 52
Joined: Thu Mar 02, 2017 8:01 am

Re: the structure does not converge

Post by weiyidan »

Thanks for your reply, as You help me a lot from last year to now.

Concerning to the problem,
1. I used POTIM=0.15, however , it did not work. I attach the calculation files in attachments and the picture shows the relationship between energy and steps. Should I use a smaller POTIM?
2.how to judge the stabilization of convergence ? is continuous decrements in energy?

Yidan Wei
weiyidan
Posts: 52
Joined: Thu Mar 02, 2017 8:01 am

Re: the structure does not converge

Post by weiyidan »

here is the attachment
Attachments
relax.rar
(2.68 MiB) Downloaded 531 times
graeme
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Re: the structure does not converge

Post by graeme »

I was not able to use the built-in IBRION=1 vasp LBFGS to obtain good convergence. My best attempt is here:
cy1.tar.gz
(44.66 MiB) Downloaded 774 times
Using quick-min (IBRION=3) did better, but did not converge within 200 iterations:
cy2.tar.gz
(27.24 MiB) Downloaded 543 times
I expect that quick-min would converge, but using our LBFGS optimizer (IBRION=3, POTIM=0, IOPT=1, INVCURV = 0.002) does a good job:
cy5.tar.gz
(20.86 MiB) Downloaded 576 times
weiyidan
Posts: 52
Joined: Thu Mar 02, 2017 8:01 am

Re: the structure does not converge

Post by weiyidan »

Thanks,professor. You really help me a lot.
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