Spectroscopic, Structure, and Thermodynamic Properties of the Lithium Cation Emerged in the Small Neon Clusters Li+-Nen (n=1-20).

The geometric structures and the relative stability of the Li +− Ne n clusters, with n = 1–20, have been computed using pairwise model potential and density functional theory (DFT) method. The potential energy surface employed in these calculations is based on the Li + -Ne, Ne-Ne and many body interactions V 3B . A series of methods and basis sets have been tested by reproduce correctly the experimental Li + -Ne and Ne-Ne potential energies. In addition, both Li + -Ne and Ne-Ne numerical potentials have been fitted by several analytical expressions as Tang and Toennies (TT), Extended Lennard Jones (ELJ) and Lennard-Jones (LJ) formula. The most stable structures of Li + -Ne n clusters up to n = 20 have been optimized at Basin Hopping Monte Carlo (BHMC) method. The accuracy of our pairwise potential model has been confirmed by re-optimization at the DFT level of theory. The relative stabilities of Li + -Ne n clusters are discussed by calculating the energy per neon atom, the first derivative, the fragmentation energy and the second derivative as well as the Highest Occupied Molecular orbital (HOMO)–Lowest Unoccupied Molecular Orbital(LUMO) energy gap with the size of the clusters. It was shown that n=6, 8, 12, 14, 16 and 17 correspond to the magic numbers. Finally, thermodynamic properties are calculated and showed that the formation process of Li + -Ne n clusters is endothermic and non-spontaneous.