Abstract
Kohn's variational method is used to calculate the positron-hydrogen scattering length and the S wave phase shifts at several energies below the positronium formation threshold, and good agreement is obtained with the results of other recent variational calculations. A detailed analysis of the structure of the zero energy wavefunction is made, and the wavefunction is used to calculate the electron-positron annihilation rate parameter Zeff, with the result 8.9, and the angular correlation of the two annihilation gamma rays. The energy dependence of Zeff is also investigated using the positive energy wavefunctions.