Physical-chemical properties of (Zn_m)@C₆₀ and (Zn_m)@C₇₀ endohedral metallofullerenes (m = 1-5): A DFT approach

The structural and electronic properties of Zn_m@C₆₀ and Zn_m@C₇₀ endohedral metallofullerenes (m = 1-5) were obtained by means of DFT calculations. The whole set of endohedral metallofullerenes (EMFs) are energetically stable despite of they are higher in binding energy than the pristine ones (C₆₀ and C₇₀). There is a structural transformation for Zn₄ and Zn₅ clusters, when these are encapsulated inside of C₆₀ and C₇₀ fullerenes; the first one changes from trigonal by-pyramid to square pyramid and the second one goes from tetrahedron to planar rhombus, respectively. This effect generates transitions on their electronic behavior, the Zn_m@C₆₀ systems exhibit two of them: from semiconductor →conductor →semiconductor and the Zn_m@C₇₀ systems present just one: from semiconductor →conductor. These electronic changes are explained by means of PDOS, HOMO and LUMO iso-surfaces and charge transference. From absorption specters, these EMFs improve the collection of visible and ultraviolet light for both cases, respect to their pristine cases. These physic-chemical properties generate potential applications such as: encapsulation of heavy metals, design of electronic devices, gases sensors and solar cells.