Theoretical investigation of the relative stability of Na⁺He(n) (n = 2-24) clusters: many-body versus delocalization effects.
The solvation of the Na(+) ion in helium clusters has been studied theoretically using optimization methods. A many-body empirical potential was developed to account for Na(+)-He and polarization interactions, and the most stable structures of Na(+)He(n) clusters were determined using the basin-hopping method. Vibrational delocalization was accounted for using zero-point energy corrections at the harmonic or anharmonic levels, the latter being evaluated from quantum Monte Carlo simulations for spinless particles. From the static perspective, many-body effects are found to play a minor role, and the structures obtained reflect homogeneous covering up to n = 10, followed by polyicosahedral packing above this size, the cluster obtained at n = 12 appearing particularly stable. The cationic impurity binds the closest helium atoms sufficiently to negate vibrational delocalization at small sizes. However, this snowball effect is obliterated earlier than shell completion, the nuclear wavefunctions of (4)He(n)Na(+) with n = 5-7, and n > 10 already exhibiting multiple inherent structures. The decrease in the snowball size due to many-body effects is consistent with recent mass spectrometry measurements.
Faculty of Sciences, Quantum Physics Laboratory, University of Monastir, Monastir 5079, Tunisia.
Noureddine
N
Issaoui
Faculty of Sciences, Quantum Physics Laboratory, University of Monastir, Monastir 5079, Tunisia.
Kawther
K
Abdessalem
Faculty of Sciences, Quantum Physics Laboratory, University of Monastir, Monastir 5079, Tunisia.
Houcine
H
Ghalla
Faculty of Science, King Abdul-Aziz University, Jeddah, Kingdom of Saudi Arabia.
Saud Jamil
SJ
Yaghmour
University of Grenoble Alpes, LIPHY, F-38000 Grenoble, France and CNRS, LIPHY, F-38000 Grenoble, France.
Florent
F
Calvo
Faculty of Sciences, Quantum Physics Laboratory, University of Monastir, Monastir 5079, Tunisia.
Brahim
B
Oujia