[lammps-users] new user questions

I am new user of LAMMPS and I have some problems with lj units.

  1. What does mean mass 1.0? How I can get the real atom mass?
  2. pair_coeff comands can define different sigma for different types.
    What sigma will be used as the distance unut?
    Thanks in advance.

You can read about LJ units in text books like Allen & Tildesley
(appendix B if I recall). Mass is unitless as well, so a mass of 1.0
is simply a standard LJ particle. Sigma = 1.0 is the distance
unit used to define the simulation box. So if some of your particles
are sigma = 2.0, then they are twice as big, etc.