CCSD(T) investigation of the interaction in neon dimer

CCSD(T) calculations on the Ne2 ground state potential have been carried out in a 240-orbital interaction optimized basis set (IO240), which contains a 3s3p2d1f1g set of mid-bond functions. The equilibrium distance (Req) and the well depth (ΔE(Req)) are 5.86 bohr and 40.99 K. The potential shows more attraction than previous ab initio potentials but there remains a difference of 1.26 K with the semi-empirical HFD-B potential of Aziz and Slaman, which is characterised by Req=5.84 bohr and ΔE(Req)=42.25 K. It is estimated that 0.5 K is missing due to basis set incompleteness, the remainder being due to the approximate description of the triples contribution and to relativistic effects.