Canuto, V., and J. Lodenquai, 1975: Solidification of neutron matter. Phys. Rev. C, 12, 2033-2037, doi:10.1103/PhysRevC.12.2033.
A new parity-conserving equation of motion is used to evaluate the ground state of a system of high density neutrons in a quantum crystal. If one form of a purely repulsive NN potential is employed, the ground state energy has a minimum with respect to the localization parameter in the density range appropriate to neutron star interiors, whereas it does not if a realistic NN potential is used. However, the values of the localization parameters αm-1 corresponding to the observed minima are very close to or even less than the separation Δ between neutrons. Since the method employed here for the solid is only reliable when αm Δ > 1, one cannot definitely say that an equilibrium solid state exists even in this case.