Hi professor,
I prepare to do a calculation than a atom moves in the surface between the two bulk.
First, i use Ediff=1e2, Ediffg=0.3, IBRION=2, it works well.
Second, i use Ediff=1e5, Ediffg =0.05, IBRION=2, it works well too.
Third, i use Ediff=1e5, 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
the structure does not converge
Moderator: moderators
the structure does not converge
 Attachments

 relax.rar
 (5.51 MiB) Downloaded 556 times
Re: the structure does not converge
Try lowering POTIM; a value of 0.3 is pretty large for IBRION=1.
Re: the structure does not converge
how about POTIM=0.15?
Re: the structure does not converge
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.
Re: the structure does not converge
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
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
Re: the structure does not converge
here is the attachment
 Attachments

 relax.rar
 (2.68 MiB) Downloaded 531 times
Re: the structure does not converge
I was not able to use the builtin IBRION=1 vasp LBFGS to obtain good convergence. My best attempt is here:
Using quickmin (IBRION=3) did better, but did not converge within 200 iterations:
I expect that quickmin would converge, but using our LBFGS optimizer (IBRION=3, POTIM=0, IOPT=1, INVCURV = 0.002) does a good job:
Using quickmin (IBRION=3) did better, but did not converge within 200 iterations:
I expect that quickmin would converge, but using our LBFGS optimizer (IBRION=3, POTIM=0, IOPT=1, INVCURV = 0.002) does a good job:
Re: the structure does not converge
Thanks，professor. You really help me a lot.