The expression for the exact ground-state energy as given by Horn and Weinstein [Phys. Rev. D 30, 1256 (1984)] is approximated using a probability distribution function having a δ function and a uniform distribution. The expression obtained up to second order does not have the singularity that one encounters in the connected-moment expansion. It also gives the same kind of expression for the ground-state energy that recently has been given by Mancini, Zhou, and Meier [Int. J. Quant. Chem. 50, 101 (1994)] when the third moment becomes negative.

• Received 26 September 1994

DOI:https://doi.org/10.1103/PhysRevA.51.1808