  A method to generate low-energy phase shifts for elastic scattering using
bound-state calculations is applied to the problem of e+ - Mg and e+ - Zn
scattering after an initial validation on the e+ - Cu system. The energy shift
between a small reference calculation and the largest possible configuration
interaction calculation of the lowest energy pseudo-state is used to tune a
semi-empirical optical potential. The potential was further fine-tuned by
utilizing the energy of the second lowest pseudo-state. The s- and p-wave phase
shifts for positron scattering from Mg and Zn are given from threshold to the
first excitation threshold. The e+ - Mg cross section has a prominent p-wave
shape resonance at an energy of about 0.096 eV with a width of 0.106 eV. The
peak cross section for e+ - Mg scattering is about 4800 a_0^2 while Z_eff
achieves a value of 1310 at an energy of 0.109 eV.
