[en] Ground-state properties of the heaviest nuclei are analyzed in the three-dimensional deformation space {β_λ}, λ=2, 4, 6. Effects of using even larger spaces are explored. Deformation, mass, alpha-decay energy and half-life of even-even nulcei with proton number Z=90-114 and neutron number N=136-168 are studied. The ground-state energy of the nuclei is treated in the macroscopic-microscopic approach. It is found that the use of a larger deformation space (in particular, a proper inclusion of the deformation β₆ in this space) significantly improves the description of experimental results and, also significantly, changes the predictions for nuclei not yet observed. (orig.)