Recently Davidson et al. [Phys. Rev. A 44, 7071 (1991)] have estimated
nonrelativistic correlation energies and relativistic corrections to
ionization potentials for atomic ions with up to 10 electrons. In this
work, this approach is extended to atomic ions with 11 to 18 electron
s. The correlation energies for 3- to 10-electron atomic ions are also
recomputed using more recent experimental and theoretical data. Unlik
e other work the method focuses on the correlation contribution to the
individual ionization energies which are obtained by comparing experi
mental data with relativistic complete-valence-space energies. Ab init
io estimates of correlation contributions to the ionization energies w
ith extensive configuration-interaction calculations of 3- to 10-elect
ron atomic ions with nuclear charge from 4 through 10 and 18, 36, 50,
72, 100, and 144 have been obtained. The correlation energies obtained
from some density-functional models are also compared to these correl
ation energy data.