Converging multidimensional rovibrational variational calculations: the dissociation energy of (HF)2

We report large scale quantum mechanical calculations for the ground state energy E0 and for the dissociation energy D0 of the HF dimer on the SQSBDE potential energy surface of Quack and Suhm. A value of 4593.13 cm−1 is obtained for E0 by a large scale variational basis set expansion and confirmed by very accurate quantum Monte Carlo calculations giving E0 of 4593.15±0.03 cm−1. The noticeably higher ground state energies computed in previous variational studies are explained by the use of suboptimal HF eigenfunctions. The new estimated value of D0 is 1058.00 cm−1.