POSITRON CHEMISTRY BY QUANTUM MONTE-CARLO - II - GROUND-STATE OF POSITION-POLAR MOLECULE COMPLEXES

The stability of the ground-state of positron-polar molecule complexes [M,e(+)] has been explored for M = LiH,HF,H2O,BeO,LiF using variation al and diffusion Monte Carlo techniques. Our simulations show that the ground-state of the complexes [LiH,e(+)](2,1)Sigma(+), [BeO,e(+)](2,1 )Sigma(+), and [LiF,e(+)](2,1)Sigma(+) is stable against the dissociat ion either in the two fragments M and e(+) or in the ether two fragmen ts M+ and Ps = [e(+),e(-)], while the ground-state of [H2O,e(+)](2,1)A (1), and of [HF,e(+)](2,1)Sigma(+) has an energy equal to the dissocia tion threshold, M and e(+). We also compare the predicted vertical pos itron affinity (PA) with high quality vertical electron affinity (EA) and discuss the relevant difference between the two values. (C) 1998 A merican Institute of Physics.