  We systematically explored the phase behavior of the hard-core two-scale ramp
model suggested by Jagla[E. A. Jagla, Phys. Rev. E 63, 061501 (2001)] using a
combination of the nested sampling and free energy methods. The sampling
revealed that the phase diagram of the Jagla potential is significantly richer
than previously anticipated, and we identified a family of new crystalline
structures, which is stable over vast regions in the phase diagram. We showed
that the new melting line is located at considerably higher temperature than
the boundary between the low- and high-density liquid phases, which was
previously suggested to lie in a thermodynamically stable region. The newly
identified crystalline phases show unexpectedly complex structural features,
some of which are shared with the high-pressure ice VI phase.
