Helium dimer potential from symmetry-adapted perturbation theory

The intermolecular potential for the helium dimer has been computed using infinite-order symmetry-adapted perturbation theory and very large orbital and explicitly correlated basis sets. Our potential is significantly deeper than recent literature potentials. After adding the relativistic retardation correction, it accurately reproduces bulk properties of helium, the inclusion of retardation being essential for this agreement. Transport properties and virial coefficients are expected to be accurate enough to calibrate measuring apparatus.