**An
improved nuclear
mass formula**,
N. Wang, *Department of
Physics, Guangxi
Normal University, China* − We propose a semi-empirical
nuclear mass formula
based on the macroscopic-microscopic method in which the isospin
and mass
dependence of model parameters are investigated with the Skyrme
energy density
functional. The number of model parameters is considerably
reduced compared
with the finite range droplet model. The rms deviation from 2149
known nuclear
masses is significantly reduced to 336 keV, even lower than that
achieved with
the best of the Duflo-Zuker models. The new magic number N=16 in
light
neutron-rich nuclei and the shape coexistence phenomena for some
nuclei have
been examined with the model. The shell corrections, the
deformations of
nuclei, the neutron and proton drip lines, and the shell gaps
are also investigated
to test the model. The alpha-decay energies of super-heavy
nuclei, the
Garvey-Kelson relations, and the isobaric multiplet mass
equation (IMME) can be
reproduced remarkably well with the model, and the predictive
power of the mass
model is good. The mirror nuclei constraint and the Wiger effect
related to the
isospin symmetry in nuclear physics plays a key role in the
improvement of mass
formula. With a systematic study of 17 global nuclear mass
models, we find that
the quadratic form of the IMME is closely related to the
accuracy of nuclear
mass calculations when the Garvey-Kelson relations are
reproduced reasonably
well. Fulfilling both the IMME and the Garvey-Kelson relations
seem to be two
necessary conditions for improving the quality of the model
prediction. The
predicted central position of the superheavy island could lie
around N=176-178
and Z=116-120 according to the shell corrections of nuclei.

[1]
N.
Wang, M. Liu and X. Wu, Phys. Rev. C **81**,
044322 (2010).

[2]
N.
Wang, Z. Liang, M. Liu and X. Wu, Phys. Rev. C **82**, 044304 (2010).

[3]
M.
Liu, N. Wang, Y. Deng and X. Wu, Phys. Rev. C **84**, 014333 (2011).