Abstract: The reasonable dissociation limit of the ground state of PH,PH+ and PH-has been achieved by the molecular reaction dynamics theory and the molecular group theory.Many methods have been used to calculate the equilibrium separation,the harmonic frequency and the dissociation energy accurately.By comparing the attained results with the experiments,the most suitable method and basis set has been gained.Based on these,the potential energy curves for the ground states of PH,PH+ and PH-have been further scanned,th...