Structures and nonlinear optical properties of the endohedral metallofullerene-superhalogen compounds Li@C60–BX4 (X = F, Cl, Br)

Abstract

It has recently been demonstrated that superatoms, which can exhibit behaviors reminiscent of atoms in the periodic table, might have synthetic utility, and represent potential building blocks for the assembly of novel, nanostructured materials [Science 2004, 304, 84–87; Science 2005, 307, 231–235; J. Phys. Chem. C 2009, 113, 2664]. In this work, a new type of endohedral metallofullerene-superhalogen compound, Li@C₆₀–BX₄ (X = F, Cl, Br), is proposed and characterized using density functional theory. The electron transfer from Li@C₆₀ to BX₄ contributes greatly to the Li@C₆₀–BX₄ compound formation. Such compounds exhibit considerable stabilities with large binding energies and ionization potentials, as well as large HOMO–LUMO gaps. The investigation of the nonlinear optical (NLO) properties of Li@C₆₀–BX₄ reveals a strong dependence of the static first hyperpolarizability, β₀, on the atomic number of the involved halogen atom X. This means that one can enhance the first hyperpolarizabilities of the endohedral metallofullerene by introducing superhalogens. The present investigation may promote the development of novel nanomaterials with unusual properties (i.e. NLO properties), and enrich the knowledge of chemical bonds (for example, long-range interactions between trapped atoms in a C₆₀ cage and the outside superatom motif).