Theoretical study of isomerism of the carbon-substituted aluminum cluster C6Al38

Abstract

Segments of the potential energy surfaces corresponding to isomers of the C6Al38 cluster with six carbon atoms located in different positions at the surface and inside the aluminum cage have been calculated by the density functional theory method. The energies and structural and vibrational characteristics of the isomers have been calculated. A distribution of the dopant as “dispersed” monatomic negative C ions located in the intermediate space between the surface and the core of the cluster and involved in C–Al bonds with both peripheral and internal metal atoms turns out to be the most favorable one. The isomers with diatomic and larger covalently bonded “subclusters” Cn are considerably higher on the energy scale and less typical. The five-coordinate carbon state (in CAl5 subclusters) with a local distorted pyramidal or bipyramidal environment is most abundant. Tetrahedral and octahedral configurations (in CAl4 and CAl6 subclusters) have also been localized but they are less abundant. Unique isomers containing complex endohedral aluminum carbide subclusters C2Al2, C3Al5, C5Al5, etc. have been localized. In most cases, the metal cage is subjected to significant distortions, in particular, axial or equatorial contraction/elongation, depending on the location of dopant atoms.