The structures of newly discovered superheavy elements with the proton numb
er Z = 110-112, 114, 116, 118 and of their alpha -decay chain nuclei are in
vestigated using the self-consistent relativistic mean-field (RMF) theory.
Extensive calculations show that the experimental data on the cy-decay ener
gies are well reproduced by the RMF theory. We find sometimes shape coexist
ence in superheavy nuclei and a superdeformed prolate configuration becomes
the ground state of the new superheavy elements. The superdeformation coul
d lead to a slightly deeper binding and give a longer lifetime for superhea
vy nuclei than expected. This may he a new mechanism for the appearance of
the superheavy island, A systematic comparison with other models for the ca
lculated binding energies and deformations is carried out, and predictions
on the properties of unknown neighbouring superheavy nuclei are made for fu
rther comparison with future experiments. (C) 2001 Elsevier Science B.V. Al
l rights reserved.