Covariant density functional theory is solved in 3D lattice space by
implementing the preconditioned conjugate gradient method with a filtering
function (PCG-F). It considerably improves the computational efficiency
compared to the previous inverse Hamiltonian method (IHM). This new method is
then applied to explore the tetrahedral shape of 110Zr in the full
deformation space. The ground state of 110Zr is found to have a
tetrahedral shape, but the deformations β31​ and β33​ greatly
soften the potential energy surface. This effect is analysed with the
microscopic evolution of the single-particle levels near the Fermi surface
driven by the deformation