Electro-Optical Properties and Structural Stability Perspectives of M3N and M2C2 (M = Sc, La) Clusters Encapsulated in B80 Fullerene: A Density Functional Theory Study

Abstract

In this work, the stability of metal nitride/carbide cluster borofullerenes, namely M3N@B80/M2C2@B80, by means of density functional theory (DFT) were evaluated. Detailed studies on M3N@B80/M2C2@B80 (M = Sc, La) series indicate that these structures have high thermodynamic and kinetic stability due to the large value of calculated embedding energies and highest occupied molecular orbital-lowest unoccupied molecular orbital (H-L) energy gaps which indicate that the Sc3N, Sc2C2, La3N and La2C2 clusters can form viable stable complexes with B80 fullerene. Our computations show the Sc3N@B80 borofullerene has the highest thermodynamic and kinetic stability and the obtained trend for thermodynamic stability is Sc3N@B80 > Sc2C2@B80 > La2C2@B80 > La3N@B80. This trend is nearly the same as obtained for the kinetic stability trend; Sc3N@B80 > Sc2C2@B80 > La3N@B80 > La2C2@B80. The H-L energy gap of Sc3N@B80 and Sc2C2@B80 are 1.45 eV and 1.39 eV respectively, much larger than La3@B80 (1.18 eV) and La2C2@B80 (1.13 eV), confirming that the nitride and carbide cluster borofullerenes have relatively high kinetic stability and could be isolated experimentally. Also, substitution of Sc with La metal in the nitride and carbide clusters imposes a noticeable influence on the stability and electronic properties of M3N@B80/M2C2@B80 structures. Analyses of electronic structure and nearest distance between clusters and fullerene reveal that both covalent and ionic interactions coexist between cluster and boron atoms. Especially in the case of La2C2@B80, the plausible electron configuration of it is [(La2C2)2−@B80 2+]. Additionally, the simulated adsorption spectra considered by means of time-dependent DFT calculations as well as circular dichroism spectra show some different absorption bands in a broad region, which is helpful to further experimental characterization. These results can promise some valuable assistance for the experimental synthesis of M3N/M2C2@B80 structures because of high thermodynamic and kinetic stability.