I am working on mechanical properties of platinum-carbon composites using MD method. There is a bond order potential field introduced by Prof. Albe ( DOI: 10.1103/PhysRevB.65.195124 ) which can represent the short ranged interaction between Pt-Pt , C-C and Pt-C. In my simulation I need to consider the long range interactions between carbon atoms. To do that, I decided to use AIREBO potential for C-C and Tersoff for Pt-Pt and Pt-C by hybrid/overlay method in LAMMPS.
To solve this issue I read the LAMMPS documentation and paper about AIREBO potential and Tersoff potential from Prof. Albe paper to understand the meaning of the parameters in both potential file. After lots of confusions, finally I understand that if I put the ‘A’ and ‘B’ parameters in potential file to zero for C C C row in tersoff file I can turn off the C-C interaction.
Do you think the whole approach is correct? I mean the potential field that I chose and the way that I am using them is correct ? I really appreciate if you have any suggestion regarding this issue.
regarding the last question, I have read the hybrid pair_style and there is an explanation as this :
Here is another example, using hybrid/overlay, to use 2 many-body potentials together, in an >>>overlapping manner. Imagine you have CNT (C atoms) on a Si surface. You want to use Tersoff >>>for Si/Si and Si/C interactions, and AIREBO for C/C interactions. Si atoms are type 1; C atoms >>>are type 2. Something like this will work:
>>>pair_style hybrid/overlay tersoff airebo 3.0
>>>pair_coeff * * tersoff SiC.tersoff.custom Si C
>>>pair_coeff * * airebo CH.airebo NULL C
Note that to prevent the Tersoff potential from computing C/C interactions, you would need to >>>modify the SiC.tersoff file to turn off C/C interaction, i.e. by setting the appropriate coefficients
to 0.0.
I read lots of literature and finally I understand that I should put A and B in CCC line to zero? But I am not sure if it is the case. Shoul I change some parameters about three body interactions?
Yes, probably setting A and B to zero will have the desired effect. But note that this is not a standard procedure, so you should verify that it is doing what you think it is doing.
So if it is not the standard way, what do you suggest in this case? I mean I have a system containing Pt, Al, C . What I understand from literatures is to use Tersoff for Pt-C and Pt-Pt, Airebo for short and long interaction of C-C and EAM for Al-Pt , Pt-Pt and Al-Al and LJ for Al-C. Do you think is there better way to define interactions which I am not aware of ?
Can I ask you again that what is the standard way of using Tersoff (Pt-C) and AIRBEO (C-C) in hybrid/overlay style? I am really confused. Consider a platinum nanocluster on a graphene sheet. Energy of adhesion ( E_Pt + E_C - E_PtC) is equal to -16.85 eV if I use Tersoff for all interactions(Pt-Pt, C-C and Pt-C). But if I use tersoff for (Pt-Pt and Pt-C, and put ‘A’ and ‘B’ for C-C-C to 0 to cancel C-C interactions from Tesoff) and Airebo (for C-C), Energy of adhesion in equal to -115.45 eV. I can not understand what is happening. please consider my request.