POSITRON AND POSITRONIUM CHEMISTRY BY QUANTUM MONTE-CARLO - III - GROUND-STATE OF [OH,PS], [CH,PS], AND [NH2,PS] COMPLEXES

The stability of the [OH,Ps], [CH,Ps] and [NH2,Ps] complexes, where Ps = (e(+),e(-)), have been studied using Monte Carlo techniques and exp licitly correlated trial wave functions. For these systems we have com puted the ground state energy values using both variational Monte Carl o and fixed node diffusion Monte Carlo methods. Diffusion Monte Carlo results allow us to predict [OH,Ps] and [CH,Ps] systems to be stable a gainst positron and Positronium (Ps) loss. As far as [NH2,Ps] is conce rned, its small value of the Binding Energy (BE) does not allow us to conclude about its stability: this is discussed qualitatively includin g zero point motion of the atoms in the complex. (C) 1998 American Ins titute of Physics.