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Covalent bonding versus total energy: On the attainability of certain predicted low-energy carbon allotropes

Görne, Arno L., Dronskowski, Richard
Carbon 2019 v.148 pp. 151-158
chemical bonding, density functional theory, energy, graphene, infrared spectroscopy, topology
On the basis of first-principles calculations, we contrast the favorable total energies of certain carbon allotropes with their uncompetitive bonding strengths as compared with those of graphite or diamond. Clearly, our tentative approach draws from ideas of organic synthesis and retrosynthesis by focusing at those bonds that have to be formed and stabilized or cleaved for preparing a certain C-based material. In particular, the covalent C–C bonds of the carbon allotropes are studied by extracting their crystal orbital Hamilton population (COHP) energies from plane-wave density-functional theory because this quantum-mechanical measure of covalent bond strength allows for a simple, yet numerically precise allotropic ranking including graphite and diamond. While many of the lowest-energy allotropes feature plainly imperfect bonding, we found a single one (topology 32.4T203 in SACADA) with both strong bonding and favorable total energy at the same time. To help experimentalists in distinguishing this very allotrope from all the other predicted carbon allotropes, we propose IR spectroscopy and predict certain vibrational fingerprints such as to identify 32.4T203 in exploratory syntheses.