  We estimate the quantum corrections to the ground state energy in neutron
matter (which could be termed as well either shell correction energy or Casimir
energy) at subnuclear densities, where various types of inhomogeneities
(bubbles, rods, plates) are energetically favorable. We show that the magnitude
of these energy corrections are comparable to the energy differences between
various types of inhomogeneous phases. We discuss the dependence of these
corrections on a number of physical parameters (density, filling factor,
temperature, lattice distortions).
