  Shape coexistence problems in N=14 isotones are studied with a microscopic
method of antisymmetrized molecular dynamics. The present calculations
reproduce features of deformation in 28Si, and predict possible shape
coexistence of neutron density in neutron-rich nuclei(19B and 24Ne). We also
systematically study the structures of the ground and excited states, and the
molecular resonances of 28Si. Besides the shape coexistence in the low-energy
region, the results indicate the high-lying levels with $\alpha$-cluster and
12C+16O molecular structures in 28Si, which are consistent with the observed
spin-assigned resonances. The resonance states above the threshold energies are
connected with the low-lying deformed states from a view point of molecular
excitation by discussing inter-cluster wave functions.
