Formation of a "Cluster Molecule" (C20)2 and its thermal stability

TL;DR

This study investigates the formation, structure, and thermal stability of a (C20)2 cluster molecule composed of two C20 fullerenes, analyzing its energy barriers and decay pathways at high temperatures.

Contribution

It introduces the concept of a (C20)2 cluster molecule with covalent bonds and analyzes its stability and decay mechanisms using the tight-binding method.

Findings

The (C20)2 cluster can exist in several isomeric forms with covalent bonds.

The open-[2+2] isomer has the lowest energy among studied configurations.

Thermal stability analysis shows decay pathways involving fullerene decay or coalescence into C40.

Abstract

The possible formation of a "cluster molecule" (C20)2 from two single C20 fullerenes is studied by the tight-binding method. Several (C20)2 isomers in which C20 fullerenes are bound by strong covalent forces and retain their identity are found; actually, these C20 fullerenes play the role of "atoms" in the "cluster molecule". The so-called open-[2+2] isomer has a minimum energy. Its formation path and thermal stability at T = 2000 - 4000 K are analyzed in detail. This isomer loses its molecular structure due to either the decay of one of C20 fullerenes or the coalescence of two C20 fullerenes into a C40 cluster. The energy barriers for the metastable open-[2+2] configuration are calculated to be U = 2 - 5 eV.