Abstract. This paper presents the application of the variable phase approach (VPA) to calculate phase shifts for various states: ³S₁ − np, ¹S₀ − nn, ¹S₀ − np, and ¹S₀ − pp using the effective range approximation potential. No free fitting parameters are used in the calculations, and a reasonably good match with the experimental phase shifts is observed for E ≤ 20 MeV, making the effective range approximation potential a strong candidate for obtaining low-energy scattering phase shifts. VPA employed is a powerful technique that bypasses the well known Schrödinger equation and does not require the wave function for SPS calculations, unlike the R-Matrix, S-Matrix, or Jost method. Interaction potentials are obtained for n-n, n-p, and p-p scattering that are exponential well-shaped.

Key words: Variable phase approach, Effective range approximation, NN interactions, amplitude functions, wave functions.