The Love-Hate Relationship Between the Shell Model and Cluster Models
  We adopt a personal approach here reviewing several calculations over the years in which we have experienced confrontations between cluster models and the shell model. In previous cluster conferences we have noted that cluster models go hand in hand with Skyrme Hartee-Fock calculations in describing states which cannot easily, if at all, be handled by the shell model. These are the highly deformed (many particle - many hole) intruder states, linear chain states e.t.c. In the present work we will consider several topics; the quadrupole moment of $^{6}$Li, the non-existence of low lying intruders in $^{8}$Be, and then jumping to the $f_{7/2}$ shell, we discuss the two-faceted nature of the nuclei - sometimes displaying shell model properties, other times cluster properties. 
Larry Zamick and Shadow J.Q. Robinson