We propose a new method of the β-γ constraint for quadrupole
deformation in antisymmetrized molecular dynamics (AMD) to describe various
cluster and shell-model structures in the ground and excited states of light
nuclei. We apply this method to N=6 isotones, 10Be, 12C, 9Li,
and 11B, and find various structures as functions of the deformation
parameters, β and γ. In these nuclei, shell-model-like structures
appear in the small β region, while cluster structures develop well in
the large β region where various geometric configurations of clusters are
obtained depending on the γ parameter. For 10Be and 12C, we
superpose the basis AMD wave functions obtained by the β-γ
constraint method to calculate energy spectra, and prove the advantages of the
present method of the two-dimensional β-γ constraint in the
framework of AMD.Comment: 23pages, 14 figure