Nucleation of a sodium droplet onC60

Abstract

We investigate theoretically the progressive coating of C60 by several sodium atoms. Density functional calculations using a nonlocal functional are performed for NaC60 and Na2C60 in various configurations. These data are used to construct an empirical atomistic model in order to treat larger sizes in a statistical and dynamical context. Fluctuating charges are incorporated to account for charge transfer between sodium and carbon atoms. By performing systematic global optimization in the size range 1 ≤ n ≤ 30, we find that NanC60 is homogeneously coated at small sizes, and that a growing droplet is formed above n ≥ 8. The separate effects of single ionization and thermalization are also considered, as well as the changes due to a strong external electric field. The present results are discussed in the light of various experimental data.

Insight into the vertical detachment energy oscillation of NanC60− clusters

“…From Na 3 C 60 − , the clustering of Na atoms starts, which was reported to start at the size of about 8 for both neutral and cationic sodium adsorbed fullerene clusters. 3,[16][17][18] The configuration for Na 3 C 60 speculated by Roques et al 18 is found to be around 0.2 eV higher in total energy for the anionic Na 3 C 60 − cluster, confirming the charge effects on the structures of small size clusters. [24][25][26][27][28] From the size of 5, the sodium aggregation configuration can be decomposed into the geometrical units of trimer and tetrahedron.…”

“…16 The segregated droplet formation of Na atoms above seven were also proposed by the empirical calculations 17 and the electric polarizability studies. 18 Recently, a density functional theory calculation 9 found a 4-atom island of Na atoms adhered to fullerene, in the line of the Na aggregation adsorption on C 60 . Besides the studies on Na aggregation, Palpant et al, based on the detailed photoelectron spectroscopy studies, proposed the packing of Na atoms of Na n C 60 − (n ≤ 12) in the form as trimer with each of the three Na atoms lying above the center of a pentagon, 6,7 being similar to the Li adsorption configuration.…”

Interaction of Impurity Atom with C<SUB>60</SUB> Fullerene Cage: A Density Functional Theory (DFT) Analysis

“…[1][2][3][4] Detailed investigations on doped fullerene molecules with dopant atoms in substitutional (where the dopant substitutes one carbon atom from the cage), endohedral (where the dopant is inside the fullerene shell), and exohedral (where the dopant is outside fullerene shells) sites of the fullerene cage have been carried out experimentally as well as theoretically. [39][40][41][42][43][44][45][46][47][48][49][50][51][52][53][54][55][56] A large number of impurity atoms including the rare gas atoms, 5-9 lanthanides 10-12 alkali metals, 10 13-19 alkali earth metal, 20-21 transition metals, [21][22][23][24][25][26][27][28] main group elements [29][30] etc., have been successfully used in the doping of fullerenes. The direct production of fullerenes in the presence of foreign species may lead to endohedral [8][9][10] or substitutional fullerenes.…”

“…Other than HF and post-HF methods, the density functional theory formalism has also been employed by several workers to obtain the information regarding the location of impurity and the interaction between impurity and fullerene molecule. [44][45][46][47][48][49][50][51] Discrete-variational local density functional calculations were performed on the endohedral NC 60 , OC 60 and FC 60 clusters by Lu et al They have found that the non-metallic N, O and F atoms are not covalently bonded to the cage and they nearly keep atomic electronic configuration unaltered. 46 Batista and co-researchers investigated the possible formation of Au-covered carbon fullerenes by means of first-principles calculations at the DFT/GGA level.…”

“…Roques et al performed for NaC 60 and Na 2 C 60 in various configurations at density functional calculations using a hybrid exchangecorrelation functional. 50 They found that sodium atom prefer to adsorb exohedrally on the position located above the center of hexagonal ring. The data obtained for NaC 60 and Na 2 C 60 were further used to construct an empirical atomistic model in order to treat large size clusters.…”