If you get bogus, large energies on timestep 0 when you run this
example in.peptide, you likely have a machine/compiler problem with
the pair_style "long" potentials which use Coulombic tabling by
default.

See the "Additional build tips" sub-section of the manual in
Section_start.html in the "Making LAMMPS" section for details and
suggestions on how to work around this issue.