Structure, electrical and nonlinear optical properties of M@C20 (M=Li, Na, K, Be, Mg and Ca) nanoclusters

The decoration of Li, Na, K, Be, Mg and Ca metal atoms on C-20 fullerene was studied using the density functional theory (DFT) method. It was shown that the structure of the fullerene was intensely affected by the metal atom present. All metal atoms have exothermic adsorption on C-20 fullerene, while Be has the highest value of adsorption energy, enthalpy and free energy. The presence of the metal atom also has a slight effect on E-g while the lowest value of E-g was obtained for Ca@C-20. The calculations of polarizability and the first hyperpolarizability show that the metal atoms highly influence fullerenes. Among metal atoms, Ca atom had the highest effect and the other metal atoms led to an increase of the first hyperpolarizability to a value of approximately 42000 a.u. The time-dependent (TD)-DFT studies showed that Ca@C-20 has the lowest excitation energies which is in agreement with the calculated first hyperpolarizability.