Robustness of the chiral-icosahedral golden shell I-Au60 in multi-shell structures.

Abstract

Motivated by the recent theoretical discovery [S.-M. Mullins et al., Nat. Commun. 9, 3352 (2018)] of a surprisingly contracted 60-atom hollow shell of chiral-icosahedral symmetry (I-Au60) of remarkable rigidity and electronegativity, we have explored, via first-principles density functional theory calculations, its physico-chemical interactions with internal and external shells, enabling conclusions regarding its robustness and identifying composite forms in which an identifiable I-Au60 structure may be realized as a product of natural or laboratory processes. The dimensions and rigidity of I-Au60 suggest a templating approach; e.g., an Ih-C60 fullerene fits nicely within its interior, as a nested cage. In this work, we have focused on its susceptibility, i.e., the extent to which the unique structural and electronic properties of I-Au60 are modified by incorporation into selected multi-shell structures. Our results confirm that the I-Au60 shell is robustly maintained and protected in various bilayer structures: Ih-C60@I-Au60, Ih-Au32@I-Au60 2+, Au60(MgCp)12, and their silver analogs. A detailed analysis of the structural and electronic properties of the selected I-Au60 shell-based nanostructures is presented. We found that the I-Au60 shell structure is quite well retained in several robust forms. In all cases, the I-symmetry is preserved, and the I-Au60 shell is slightly deformed only in the case of the Ih-C60@I-Au60 system. This analysis serves to stimulate and provide guidance toward the identification and isolation of various I-Au60 shell-based nanostructures, with much potential for future applications. We conclude with a critical comparative discussion of these systems and of the implications for continuing theoretical and experimental investigations.