Ground state potential energy surfaces and bound states of M–He dimers (M=Cu,Ag,Au): A theoretical investigation

Abstract

We present an ab initio investigation on the ground state interaction potentials ͓potential energy surface ͑PES͔͒ between helium and the group 11 metal atoms: copper, silver, and gold. To the best of our knowledge, there are no previous theoretical PESs proposed for Cu-He and Au-He, and a single one for Ag-He ͓Z. J. Jakubek and M. Takami, Chem. Phys. Lett. 265, 653 ͑1997͔͒, computed about 10 years ago at MP2 level and significantly improved by our study. To reach a high degree of accuracy in the determination of the three M -He potentials ͑M =Cu,Ag,Au͒, we performed extensive series of test computations to establish the appropriate basis set, the theoretical method, and the computational scheme for these systems. For each M -He dimer we computed the PES at the CCSD͑T͒ level of theory, starting from the reference unrestricted Hartree-Fock wave function. We described the inner shells with relativistic small core pseudopotentials, and we adopted high quality basis sets for the valence electrons. We also performed CCSDT computations in a limited set of M -He internuclear distances, adopting a medium-sized basis set, such as to define for each dimer a CCSD͑T͒ to CCSDT correction term and to improve further the quality of the CCSD͑T͒ interaction potentials. The Cu-He complex has minimum interaction energy ͑E min ͒ of −28.4 hartree at the internuclear distance of 4.59 Å ͑R min ͒, and the short-range repulsive wall starts at 4.04 Å ͑R E=0 ͒. Quite interestingly, the PES of Ag-He is more attractive ͑E min = −33.8 hartree͒ but presents nearly the same R min and R E=0 values, 4.60 and 4.04 Å, respectively. The interaction potential for Au-He is markedly deeper and shifted at shorter distances as compared to the lighter complexes, with E min = −69.6 hartree, R min = 4.09 Å and R E=0 = 3.60 Å. As a first insight in the structure of M -He n aggregates, we determined the rovibrational structure of the three M -He dimers. The Cu-He and Ag-He potentials support just few rotational excitations, while the Au-He PES admits also a bound vibrational excitation.

Formation and dynamics of van der Waals molecules in buffer-gas traps

“…2, alongside the prediction using the potentials of Ref. 52. We observe that κ(T ) is very sensitive to fine details of the ab initio interaction potentials.…”

“…The overall magnitude of the calculation underpredicts the experimental data, but this can be explained by increasing the binding energy to 1.53 cm −1 , a 10% larger value than we predict. However, we note that the AgHe potential of Cargnoni et al 52 also predicts a binding energy of 1.53 cm −1 . This adjusted result is compared to data in Fig.…”

“…Potentials for this system have previously been constructed 52,59 in the studies of the AgHe* exciplex. An accurate potential has also been constructed 60 during the production of this article.…”

Energetics of pure and doped helium droplets - application to interpreting pick-up experiments

“…We note that these calculations employ an Ag-He pair potential given by Cargnoni et al, 24 which predicts a slightly (0.9 K) deeper well minimum than the Ag-He potential used in this work. FIG.…”

Phonon generation in condensed 4 He by laser-excited atomic bubbles

“…(2) for the Cu atom in liquid He (dotted curve). The corresponding p a (R b ) is calculated using the Cu-He pair potential from [27]. The ground-state atomic bubble has a radius of 4.0Å that is significantly smaller than R b for Cs.…”