[lammps-users] Error due to fix rigid for larger group

Hi all,

Here is the description of my problem:

  1. Modeled a Smaller sphere say of approximately 3 nm and used fixed rigid for the atoms.
  2. Made this sphere interact with a rectangle using LJ potential between the sphere and the rectangle.
  3. The simulations ran sucessfully and the results make sense.

But when I tried to model a larger sphere say of approximately 10 nm and used fixed rigid for the atoms, during the simulation, it returned an error “BAD PRINCIPAL MOMENTS”. I would like to know what could be done to overcome this error, as I need to run a case of 30 nm sphere in the future.

Thanks in advance,


You could try reducing the TOLERANCE variable at the top of fix_rigid.cpp
(and re-compiling). If you search for the error text you'll see where the
computed moments are compared to tolerance. I don't know why you
would have this problem for a large sphere. How many atoms in your
rigid sphere? We've done 50K rigid atoms before w/out problem.