LAMMPS data file 

4 atoms 
0 bonds

3 atom types 
1 bond types
1 extra bonds per atom

-20 20 zlo zhi 
-20 20 ylo yhi 
-20 20 xlo xhi 

 Masses 

1 1
2 1 
3 1

 
 Atoms 

1 1 1 -1.0 0.001 -1.0
2 1 1 -1.0 0.001 0.0
3 1 1 -1.0 0.0 -1.0
4 1 1 -1.0 0.0 0.0


Bonds
1 1 3 4
2 1 1 2