Dear everyone, I am trying to modify the Au_u3.eam and Cu_zhou.eam.alloy potential for cascade simulation. Referring to some references, I followed the method using Fermi function to modify the potentials, which can be expressed as Vtot(r)=VZBL(r)(1-F(r))+Veq(r)F(r) and F(r)=1/(1+e-bf(r-rf)), F(r) is named Fermi function. My results are shown in the attachments. In my case, the Veq(r) represents the pair-style potential phi in eam or eam/alloy potential and the F and rho is not modified. The blue lines represent the pair-style potential phi of the original eam or eam/alloy potential (Veq(r)), green lines ZBL potential (VZBL(r)) and red lines pair-style part of modified potential (Vtot(r)), respectively.
My questions are:
(1) According to the pictures, could you please tell me whether my modified potential is suitable for cascade simulation?
(2) What should I do to check whether the potential is ready for cascade simulation? Could somebody tell me what quantities should be calculated and checked? And give me some instructions on how to check them.
Any suggestion would be very helpful. Thanks very much!
Hi.
For the first question, I see the red line (modified potential) has a steeper gradient than the ZBL, which implies that more energy will be transferred per collision event that if you were to use the ZBL potential (more force due to steeper gradient). Typically when interpolating between a repulsive potential and the ZBL potential you must choose the bounds of the interpolation such that the re is no such steep gradient.
Regarding the second question, check out how much (a) the the number of displaced atoms, (b) the volume of the collision cascade and (c) defect clustering, changes with the modified and um-modified potentials.
Best Regards
Manoj
Hi Manoj. Thanks a lot for your reply.
I still have one question about your answer to my first question. You said that “Typically when interpolating between a repulsive potential and the ZBL potential you must choose the bounds of the interpolation such that the re is no such steep gradient.” Did you mean my modified potential is not good enough for cascade simulation and I need to modify this with another method? Could you please explain this? And the word “re” mean in you sentence?
Thanks very much!
Hi.
It was not meant to be "the re" it was "there".
As regards the goodness of the modified potential, check out the answer to your second question. If those values do not change much, it is good enough.
Hi Manoj. I got the idea.
It is very nice of you to help. Thank you very much!
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