Coexistence of pure octupole shapes in the superheavy nucleus ²⁸⁶No

The shape of ²⁸⁶No is investigated with the relativistic density functional theory on a three-dimensional lattice space without any symmetry restriction in a microscopic and self-consistent way. It is found that the ground state of ²⁸⁶No has a pure non-axial octupole shape and coexists with a tetrahedral isomeric state. The energy difference between the two states is only 0.12 MeV, and they are separated by a potential barrier of about 0.5 MeV. The occurrence of the octupole correlations is analyzed with the evolution of the single-particle levels near the Fermi surface driven by the octupole deformations.