 
Summary: An exact quantum Monte Carlo calculation of the heliumhelium
intermolecular potential
James B. Anderson
Department of Chemistry, The Pennsylvania State University, University Park, Pennsylvania 16802
Carol A. Traynor
Department of Chemistry, Harvard University, Cambridge, Massachusetts 02138 and Thinking Machines
Corporation, Cambridge, Massachusetts 02142
Bruce M. Boghosian
Thinking Machines Corporation, Cambridge, Massachusetts 02142
(Received 15 December 1992; accepted 25 March 1993)
We report "exact" ab initio calculations of potential energies for the interaction of two helium
atoms. The quantum Monte Carlo method used is exact in that it requires no mathematical or
physical approximations beyond those of the Schriidinger equation. As in most Monte Carlo
methods there is a statistical or sampling error which is readily estimated. For the equilibrium
internuclear distance of 5.6 bohr, the calculated electronic energy is  5.807 483 6 f 0.000 000 3
hartrees and the corresponding well depth (e/k) is 11.01 f 0.10 K. The calculated total energies
are approximately 0.004 hartrees or 1200 K below the most recent variational calculations of
Liu and McLean [J. Chem. Phys. 92, 2348 (1989)]. The calculated interaction energies are in
excellent agreement with the interaction energies of Liu and McLean and with a recent
experimental/theoretical compromise potential energy curve of Aziz and Slaman [J. Chem.
