The properties of the Be isotopes are studied by the deformed Hartree-Fock method with Skyrme interactions. It is shown for ${}_{}{}^{11}{}_{}{}^{}\mathrm{Be}$ that the configuration where the last neutron occupies a ${\mathit{K}}^{\mathrm{\pi }}$=1/$2^{+}$ orbital is not the ground state but has a matter density distribution with a tail typical of a halo nucleus. Correlations are introduced in deformed mean-field wave functions by a restoration of rotational invariance. These correlations bring the amount of energy necessary to correct the deficiencies of pure mean-field wave functions. © 1996 The American Physical Society.

• Received 29 January 1996

DOI:https://doi.org/10.1103/PhysRevC.54.1617