A self-contained and tutorial presentation of the diffusion Monte Carlo
method for determining the ground state energy and wave function of quantum
systems is provided. First, the theoretical basis of the method is derived and
then a numerical algorithm is formulated. The algorithm is applied to determine
the ground state of the harmonic oscillator, the Morse oscillator, the hydrogen
atom, and the electronic ground state of the H2+ ion and of the H2 molecule. A
computer program on which the sample calculations are based is available upon
request.