Need help regarding a project

I am trying to simulate Friction stir welding on an Al-Cu bi-layer using LAMMPS, I am very new to this software and thus have very little knowledge of working with it. Using some examples and papers on the topic, I managed to create a box with an Al-Cu bi-layer. Now I want to create a carbon tool that would work as the rotating tool (similar to the tool in FSW). I get some errors when I fix the boundary conditions as fixed for two axes (error of atom loss) and also have no idea on how to proceed with the tool part(cylindrical tool and the linear velocity and rotational velocity for the tool). Kindly help me with these.

Please understand that you have two kinds of problems:

  • problems specific to LAMMPS and its syntax and errors
  • problems in how to implement your specific research project

This forum can help you with the former, but not (much) with the latter.

Also, to get help you have to ask more specific questions and provide specific examples. It is usually best to not just attach your research project, but rather construct minimal and simplified examples that apply only parts of the project or use a simpler/smaller setup/system so that it can be run quickly and also only exhibits one specific issue that you want to ask about. Having all kinds of variables and convenience expressions in there only makes it more effort to evaluate and thus less likely to get help.

With this approach you can break down your collections of problems into small, manageable individual problems and resolve them one at a time. You may also try to search the web and will find that there always have been people new to LAMMPS and many have similar problems, so you may already find responses and suggestions that you can apply after confirming with the manual that those are still applicable and with the correct syntax (these things can change over time so checking with the manual is essential).

Thank you for the reply, I have got various insights and ways to approach the problem after your detailed answer and will surely implement them in the future course of this project.

As you mentioned that I should be specific with the problems, so currently I am struggling with giving a specific set of atoms a linear velocity and a rotational one too. Is there any specific set of commands in LAMMPS which would help me with these?