Contributions from high-order (non-perturbative triple and quadruple) cluster amplitudes to the dissociation energies, equilibrium distances, and vibrational constants for the ground states of van der Waals dimers Hg2 and Cn2 are evaluated. The incorporation of these contributions into the results of large-scale CCSD(T) calculations leads to non-negligible corrections of the computed molecular constants for Hg2 (6% for the dissociation energy), and enables one to attain perfect agreement with the experimental values.
@article{arxiv.1001.2046,
title = {Correlations beyond CCSD(T) for accurate study of Hg$_2$ and Cp$_2$},
author = {A. N. Petrov and N. S. Mosyagin and A. V. Titov and A. V. Zaitsevskii and E. A. Rykova},
journal= {arXiv preprint arXiv:1001.2046},
year = {2010}
}