| The nuclear clustering structure becomes an important subject of nuclear physics. In particular, the clustering structure of light nuclei becomes a hot topic. Many theoretical and experimental researches show that the clustering structure is the fundamental characteristics of light nuclei, it is more likely to occur in N=Z or their neighboring nuclei and even in the drip-line nuclei. The possible clustering formations contain linear chain, octupole, triangle, ring-like and flower-like shapes. Specifically, the a clustering structure is known to play a key role in some nuclei, such as Be isotopes,12C,16O,20Ne,28Si,40Ca, and so on. Experimentally the information on clustering structure can be obtained by inelastic scattering, break-up and knock-out reactions. On the theoretical side, clustering structure has been studied extensively with many models, including microscopic cluster model (resonating group method (RGM), generator coordinates method (GCM), orthogonality condition method (OCM), stochastic variational method (SVM), molecular orbital (MO) model, antisymmetrized molecular dynamics (AMD) model), fermion molecular dynamic (FMD) model, effective liquid drop model (ELDM), density-dependent cluster model (DDCM) and covariant density functional.The point-coupling covariant density functional has achieved great success in describing properties for nuclei all over the periodic table. The point-coupling covariant density functional has attracted more and more attention due to the following advantages. First, there is no mesonic degree of freedom which makes the amount of numerical calculation considerably reduced. Second, it can be easily extended to investigate beyond the mean-field approximation for nuclear low-lying excited states.Based on the point-coupling covariant density functional, the ground-state properties and clustering structure of light nuclei were investigated. The light nuclei include even-mass Be isotopes, N=Z nuclei (12C,16O,20Ne,24Mg,28Si,32S,36Ar,40Ca), drip-line nuclei (32Ne,48S,52Ar,58Ca), even-mass Mg isotopes and N=12nuclei (18C,20O,22Ne). The ground-state properties include the calculated binding energies, quadrupole deformation parameters, the corresponding root-mean-square (rms) radii and pairing energies. Pairing correlations are taken into account by using the Bardeen-Cooper-Schrieffer (BCS) approximation with zero range. The properties of light nuclei were studied with the effective interactions PC-F1and PC-PK1.First, the research on the potential energy surfaces, ground-state properties, density distributions and single-particle energy levels of even-mass Be isotopes have been performed in the respects of pairing correlations, effective interaction parameters and nucleon numbers. The results are composed of four aspects:(1) Pairing correlations have a great influence on the potential energy surfaces, ground-state properties and density distributions of even-mass Be isotopes.8,10,14Be have the2a clustering structure without pairing correlations, but8,14Be have the2a clustering structure with pairing correlations. Pairing correlations could weaken the2a clustering structure of even-mass Be isotopes;(2) PC-F1and PC-PK1effective interactions have little impact on the potential energy surfaces, ground-state properties and density distributions of even-mass Be isotopes;(3) The2a distances and the corresponding quadrupole deformation parameters have a similar evolution trend against the neutron number;(4) The larger energy gaps around the Fermi surface in the single particle levels, the more clustering structure is revealed.Second, similar to the method we did it before, a trial research is made on the other nuclei, including the potential energy surfaces of4Mg, ground-state properties of N=Z and drop-line nuclei, observables of constraint calculation of24Mg and density distributions. The conclusions of this study are as follows:(1) Pairing correlations can have a significant impact on the ground-state properties and density distributions of36Ar and40Ca;(2) PC-F1and PC-PK1effective interactions strongly affect the clustering structure of N=Z nuclei, but less affect the clustering structure of drop-line nuclei;(3) The influences in nucleon number increase on clustering structure: a. The clustering distances of two centers of even-mass Mg isotopes and the corresponding quadrupole deformation parameters have the same varying tendency; b. A much greater effect on clustering structure of increasing the number of neutrons rather than the number of protons;(4) The same nucleus with different quadrupole deformation parameters has a different clustering structure;(5) The depth of single-nucleon potential and the corresponding single-nucleon densities have the extreme values at the same time. The clustering structure is most evident when the depth of single-nucleon potential is deepest. |
