 
Summary: An exact quantum Monte Carlo calculation of the heliumhelium
intermolecular potential. II
James B. Andersona)
Department of Chemistry, Pennsylvania State University, University Park, Pennsylvania 16802
Received 19 March 2001; accepted 19 June 2001
We report ``exact'' ab initio calculations with reduced statistical error for the potential energy of
interaction of two helium atoms. For the equilibrium internuclear distance of 5.6 bohr, the calculated
electronic energy is 5.807 483 53 0.000 000 06 hartrees and the corresponding well depth is
( /k) 10.98 0.02 K. © 2001 American Institute of Physics. DOI: 10.1063/1.1390512
Several years ago we reported ``exact'' quantum Monte
Carlo QMC calculations of potential energies for the inter
action of two helium atoms.1
For the equilibrium internuclear
distance of 5.6 bohr, the calculated interaction energy was
11.01 K with an uncertainty of 0.10 K 1 . Using new
computers about a factor of 100 faster than before we have
repeated the earlier calculations with a larger number of
samples to obtain a new value of 10.98 K with an uncer
tainty of 0.02 K 1 . The uncertainties of other points
along the potential energy curve have been similarly re
