Issue with Setting Potentials for Cu-Si Hybrid System

Hello everyone,
I’m currently simulating a Cu-Si hybrid system and intend to use different potentials to describe Cu-Cu, Si-Si, and Cu-Si interactions. Specifically, I plan to use the eam/alloy potential for Cu-Cu interactions and the tersoff potential for Si-Si and Cu-Si interactions.
In my input file, I’ve set up the potentials as follows:
pair_style hybrid tersoff eam/alloy tersoff
pair_coeff * * tersoff SiCu.tersoff Cu Si
pair_coeff * * eam/alloy Cu01.eam.alloy Cu NULL
pair_coeff * * tersoff 2 SiC.tersoff NULL Si
Unfortunately, I’m not getting the expected simulation results, and it seems there might be an issue with the potential settings. I’d like to seek guidance from the forum - is there anyone who can help me understand how to correctly set up potentials for this hybrid system? Are there possible oversights or errors in my pair_coeff settings?I need to modify the parameters in the SiCu.tersoff file to 0.0 to exclude the interaction between Cu-Cu and Si-Si in the first pair_coeff, right?
Thank you all for your assistance!
Best regards.

This is a very, VERY bad idea.

First, these are all manybody potentials, so you cannot divide them by pairs of atom types. That only would work with pairwise additive potentials.

Second, if you have potentials that are optimized for the mixed case, why try to replace parts of it with parameters that have been optimized for a different application and use case. That must lead to less accurate and inconsistent results.

Finally, the LAMMPS hybrid pair style does not have provisions to support manybody potentials with “overlapping pairs”. Each manybody potentials must be restricted to “complete” set of atom types and the “mixed” pairs must be implemented with pairwise additive potentials.

In general, using hybrid makes the most sense for pairwise additive potentials (but even then it is frowned upon) or systems where you have well separated groups of materials (e.g. a block of copper and a block of silicon, e.g. in a nanomachining type of setup).

Thank you for your suggestions and insights.

I appreciate the points you raised, especially regarding the characteristics of many-body potentials and the consistency of optimized parameters. I am considering reassessing my simulation approach to ensure more accurate and reliable results.