  We introduce a microscopic approach to derive all the inertial functions in
the five-dimensional quadrupole collective Hamiltonian. Local normal modes are
evaluated on the constrained mean field in the quasiparticle random-phase
approximation in order to derive the inertial functions. The collective
Hamiltonians for neutron-rich Mg isotopes are determined with use of this
approach, and the shape coexistence/mixing around the N = 20 region is
analyzed.
