Positronium binding to potassium and other alkali atoms

The fixed-core stochastic variational method has been used to demonstrate the existence of an electronically stable ground state for potassium positride, KPs, with a binding energy of 0.003 275 Hartree. The 2 annihilation rate of 2.001 × 109 s-1 was almost the same as the annihilation rates computed previously for LiPs and NaPs. Analysis of the radial expectation values, the annihilation rates and the e--e+ correlation function reveal that KPs can be regarded as a Ps cluster moving in the field of the neutral atom.