2D-ordered kinked carbyne chains: DFT modeling and Raman characterization

During the past years one-dimensional carbon allotropes containing sp1 bonds, both individual chains and carbyne-like crystals held by Van der Waals forces, were attracting much interest. One of the recent developments is the ion-assisted condensation of sp1 chains, ordered in a hexagonal structure with nearly 5 Å interchain distance - 2D-ordered linear-chained carbon (LCC). The main problem of LCC synthesis is the lack of simple characterization technique rapidly confirming its structural features. In the present work, for the first time the experimental Raman spectra of the LCC films and ab initio calculation of Raman susceptibilities using the simple structural model of LCC are combined to provide the Raman bands identification and to propose a rapid characterization technique. DFT calculations establish dependence between linear fragment length, kink angle and Raman-active phonon modes of carbon chains, giving interpretation to high frequency and low frequency vibrations, taking into account the distribution of LCC structural parameters. The calculation results explain the inversion of single-chain Raman spectrum occurring in case of chains ensemble by the interaction between chains, enhanced by the kink-related charges in the LCC structure.

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