[lammps-users] Unbalanced angular momentum: a bug?


I am trying to equilibrate a spherical core (12.27 angstrom in radius) of 441
silver atoms, using EAM potential. The initial temp I have set is 500 K.

I used the following velocity command to nullify the aggregate angular

velocity all zero angular

Yet, I found an unbalanced rotational motion in the YZ plane (though not in
the XY or XZ plane)!

Only when I additionally used the following fix command did I get zero angular
momentum in all three planes with just oscillatory motion about respective
mean positions.

fix 2 all momentum 100 angular

Could you please suggest why this fix command is needed in spite of setting
the angular momentum to zero using the velocity command. Is this a
characterictic of the EAM potential or a possible bug?

Again, your help would be highly appreciated.

I am pasting below my piece of code (with the second fix commented).

This was indeed a bug in the angular momentum routine for velocity
creation (but not for fix momentum). I posted a patch, 16Aug07.