Ground state of positronium hydride

The ground bound state in the positronium hydride molecule (HPs) is determined from extensive variational four-body calculations with the James-Coolidge four-body variational expansion in the relative coordinates r(12), r(13), r(23), r(14), r(24), and r(34). For the positronium hydride with the infinitely heavy nucleus ((infinity)HPs) the total energy found, E = -0.789 1369 a.u., is one of the lowest variational values published to date. A number of bound-state properties have been calculated also, including the delta-function expectation values, two-body cusps, and the two-photon annihilation rate.