Prediction of standard enthalpies of formation of boron nitride nanocones

Authors: FAHIMEH SHOJAIE

Abstract: Prediction of the standard enthalpy of formation (Δ_fH⁰₂₉₈) of boron nitride nanocone (BNNCs) structures with disclination angles 60°, 120°, and 180°is recommended to be performed by the isodesmic reaction approach. NH₃, BH₃, and N₂H₄ were selected as key reference compounds. In order to calculate Δ_fH⁰₂₉₈ of nanocones, we must first calculate the enthalpies of nanocone rings at their apexes. For this purpose, Δ_fH⁰₂₉₈ values of 40 different structures, such as boron, nitrogen, and hydrogen compounds, have been calculated by combining Gaussian-4 (G4) theory calculations with the isodesmic and other balanced reactions approach. At each stage of the calculations, the previously estimated enthalpies of formation of nanocones were used as reference points for new molecules in the isodesmic and other balanced reactions. The results of enthalpies of formation of reference compounds were then used as reference values to estimate the enthalpy of formation of rings of BNNCs at their apexes. Finally, enthalpies of formation of BNNCs with disclination angles of 60°, 120°, and 180°and cone heights of 1-5 Å, 3-7 Å, and 4-8 Å were calculated. The results show that the reactions are highly exothermic. An increase in cone height causes the enthalpy of formation of boron nitride nanocone structures to become more negative.

Keywords: Boron nitride nanocones, enthalpy of formation, isodesmic approach, reference compounds, Gaussian-4 (G4) theory calculations

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