[lammps-users] Inertia x, inertia y and inertia z not matching with what calculated from compute rigid/local

Dear all,
I analytically calculated the I_xx, I_yy and I_zz for the rigid body composed of two spheres( just touching no overlap). Below are the coordinates(global ref frame) of the spheres and they both have the same radius 0.5

3.51543 21.8857 7.20197
4.51543 21.8857 7.20197

I found I_xx=0.10471975511966; I_yy=I_zz=0.366519142918809

whereas from ''compute rigid/local inertiax inertiay inertiaz ‘’

I am getting I_xx=I_yy=0.366519142918809; I_zz=0.10471975511966

which is quite the opposite. Help is much appreciated

Best regards
Saikat

They seem to be the same but just viewed from a different orientation. You probably have chosen a different principal axis than LAMMPS has done internally.

axel.