My question is related to LJ-potential for Metals. I tried to use LJ potential with appropriate parameters for Fe. In order to hold the atoms together I apply a fix spring command to tether the group of Fe atoms. Still I observe that atoms tend to migrate away from their region, much like fluids behave when used with LJ potential. I have applied high values of spring constant in the tether but not much help. I have found papers on MD where metals have been modeled with LJ potential parameters. It would be great if someone can highlight on how I can go about this and where can I make changes so that I get better results.