Diffusion quantum Monte Carlo calculations of positronium hydride and positron lithium

The diffusion quantum Monte Carlo (QMC) method is applied to the calculations of the binding energies of the positronium hydride, S-1,S-2[e(+)-H-], and the positron lithium, S-2,S-1[e(+)-Li]. The QMC binding energy of the positronium hydride system is found to be in excellent agreement with the recent experimental value. The result of the energy of the positron-lithium system suggests that it is stable with respect to positron dissociation, but is probably unstable compared to separated Pa and Li+.