  We consider a one-dimensional classical many-body system with interaction
potential of Lennard-Jones type in the thermodynamic limit at low temperature
$1/\beta\in(0,\infty)$. The ground state is a periodic lattice. We show that
when the density is strictly smaller than the density of the ground state
lattice, the system with $N$ particles fills space by alternating approximately
crystalline domains (clusters) with empty domains (voids) due to cracked bonds.
The number of domains is of the order of $N\exp(- \beta e_\mathrm{surf}/2)$
with $e_\mathrm{surf}>0$ a surface energy.
  For the proof, the system is mapped to an effective model, which is a
low-density lattice gas of defects. The results require conditions on the
interactions between defects. We succeed in verifying these conditions for
next-nearest neighbor interactions, applying recently derived uniform estimates
of correlations.
