Composite nanosystems such as cluster interfaces can have interesting and potentially useful properties, possibly different from those of the corresponding counterparts in both the molecular and macro-scale limits. Here we study mixed-composition species representing interfaces at the molecular level between such technologically relevant materials as carbon and aluminum. Specifically, core−shell C8@Aln (n = 16,18) species and their C8Aln isomers with the core and relaxed-shell attached externally are investigated at a DFT level in terms of structures and stabilities, charge distributions and polarities, IR spectra, electron affinities and ionization potentials, reactivity parameters. Among interesting findings is the possibility of stabilizing and shaping the aluminum cluster into a more symmetric structure (thus making a convenient potential building block) via insertion of a suitable molecular-carbon skeleton or even its attachment from outside. In particular, the systems exhibit a correlation in closing the atomic (aluminum) and electronic shells. Another notable feature is the system-selective dependence of polarity on spin multiplicity, suggesting possible molecular−electronic applications. The IR spectra of the composite species are much brighter compared to those of the separated components and are highly focused for the core−shell isomers. A related aspect of interest is the apparent reflections of the system structural details in the IR spectra features (line intensities and separations) via related vibrations, facilitating an experimental analysis of the structure and detection of the species formation and transformation as well as potentially enabling the means of achieving desirable optical characteristics via a geometric design. At the same time, the reactivity of the aluminum component is estimated to be affected rather weakly by the carbon-core doping.

Symmetrization of structure and enhancement of IR spectra of aluminum clusters by carbon-core doping

ACS Spring 2022

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