Positronium binding to potassium and other alkali atoms

The fixed-core stochastic variational method has been used to demonstrate t he existence of an electronically stable ground state for potassium positri de, KPs, with a binding energy of 0.003 275 Hartree. The 2 gamma annihilati on rate of 2.001 x 10(9) s(-1) was almost the same as the annihilation rate s computed previously for LiPs and NaPs. Analysis of the radial expectation values, the annihilation rates and the e(-)-e(+) correlation function reve al that KPs can be regarded as a Ps cluster moving in the field of the neut ral atom.