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???156Nd isotopes. It is found that, within the M scheme, the systems with the number N?? = 7 of neutron pairs (or the number N?? = 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???156Nd isotopes may be a good candidate for the first-order shape phase transition.