Compact wave functions for the beryllium isoelectronic series, Li- to Ne6+: a standard Hylleraas approach.

Variational calculations have been carried out for the ground states of several members of the beryllium isoelectronic series using a standard Hylleraas approach involving Slater-type basis functions. The species examined are Li(-), Be, B(+), C(2+), N(3+), O(4+), F(5+), and Ne(6+). For each species, the nonrelativistic energy, the electronic density at the nucleus, the expectation value <∇(i)·∇(j)>, the moments <r(i)(n)> for n = -1, 1, 2, and 3, and <r(ij)(n)> for n = -1, 1, and 2, are reported. With relatively compact basis sets, the ground state energies are obtained with uncertainties ranging from 50 parts per million to just under 4 parts per million.