 
Summary: Quantum chemistry by random walk: Higher accuracy for H3+
James B. Anderson
Department of Chemistry, The Pennsylvania State University, University Park, Pennsylvania 16802
(Received 28 October 1991; accepted 22 November 1991)
An improved quantum Monte Carlo calculation for the ground state of the molecular ion H;t
gives higher accuracies than previously attained. The nonrelativistic electronic energy for the
equilateral triangle configuration of side length 1.6500 bohrs is found to be
 1.343 835 + &OO 001 hartrees.
1.INTRODUCTION
Since Hirschfelder's' first analytic variational calcula
tion of the electronic energy of the molecular ion H3+, there
has been a succession of improved calculations which illus
trate the advance of theoretical chemistry to higher and
higher accuracies. 2d' Calculations for the equilateral trian
gle nuclear configuration of H: near the equilibrium inter
nuclear distance of approximately 1.6500 bohrs are listed in
Table I and their energies are plotted in Fig. 1. The progress
of analytic variational calculations may be followed toward
lower and lower energies, approaching with time the exact
value. The progress of quantum Monte Carlo calculations
