oft
Coulomb style = smooth should be used with nonbond style = lj/smooth,
  and both should use same inner and outer cutoffs
nonbond style = lj/charmm should be used with coulomb style = charmm/switch
for smooth and charmm/switch styles, outer cutoff must be &gt; inner cutoff
for smooth and charmm/switch styles, atom pairs less than the inner cutoff
  distance use usual Coulomb, pairs between inner and outer are smoothed,
  and the potential goes to 0.0 at the outer cutoff
for smooth style, force is continu