1    Argon
#   id  name    x   y   z   bonds#  bonds   
    1   Ar      0   0   0   0

# parameters
# keyword atomname mass charge no of neighbours comment
atom      Ar       1.0  0.0    0                "liquid argon" 

# keyword   atom list       epsilon sigma
vdw         Ar  Ar          1.0     1.0