Even-even Nd isotopes in an SD -pair shell model

Nucleon pair shell model truncated to $SD$ collective pair subspace (SDPSM) was applied to study the properties of the low-lying states of the even-even $^{144--156}\mathrm{Nd}$ isotopes. It is found that, within the $M$ scheme, the systems with the number ${N}_{\ensuremath{\nu}}=7$ of neutron pairs (or the number ${N}_{\ensuremath{\pi}}=7$ of proton pairs) can be studied in the SDPSM for the first time. The results show that the properties of the low-lying states of the even-even Nd isotopes can be reproduced approximately, and the even-even $^{144--156}\mathrm{Nd}$ isotopes may be a good candidate for the first-order shape phase transition.