Dear LAMMPS users,

I’m not exactly sure of where to post this and that’s why I’m posting in the general discussion. So, I’m studying anisotropic diffusion of the COM of an organic molecule and as a result need to convert the COM in the world frame to body frame. My understanding is that compute com/chunk calculates in world frame, but I can’t find a compute in LAMMPS that does this in body frame.

As a result, I’m planning to post process by calculating the moment of inertia of the molecules in LAMMPS, obtain the eigenvector (corresponding to the biggest eigenvalue) and calculate the angle that this eigenvector makes with the simulation box’s x-axis. This angle will then be fed into my rotation matrix (for rotation in x-y plane)

Where I need clarification with is this:

- When LAMMPS calculate moment of inertia, does it translate the origin to the COM of the molecules?
- If it does, how can one obtain this displacement vector?
- Is there a more efficient way to do this whole coordinate transformation in LAMMPS?

Thanks a lot.