Exploring Local Reactivity of Large Systems through Combining Conceptual DFT and the GFN2-xTB Method.

Abstract

This study evaluates the ability of the GFN2-xTB method and Conceptual Density Functional Theory-derived tools to predict local reactivity in large systems. Carbon-based systems such as C₆₀, C₇₀, Li⁺@C₇₀, C₂₄₀, C₃₆₀, C₆₄₈, and C₇₂₀ have been used as test sets, and the orbital-weighted dual descriptor was employed to identify nucleophilic and electrophilic regions, providing a comprehensive analysis of their reactivity patterns. The results confirm that the GFN2-xTB method accurately reproduces reactivity profiles observed experimentally and at the DFT level, particularly in well-known fullerenes like C₆₀ and C₇₀. The addition of an endohedral Li⁺ cation to C₇₀ demonstrated enhanced electrophilicity and reduced unfavorable nucleophilic regions, consistent with previous studies. For larger and less-studied systems, such as C₂₄₀, C₃₆₀, C₆₄₈, and C₇₂₀, the analysis revealed distinct reactivity features, including the localization of nucleophilic regions in -C≡C- units of C₂₄₀/C₆₄₈, the nucleophilic regions at the ends of the C₃₆₀ nanoparticle model, and the emergence of electrophilic zones due to the reduction in aromaticity of the benzenoid rings in C₇₂₀. These findings validate the GFN2-xTB method as a computationally efficient alternative for exploring the reactivity of large structures and contribute valuable insights into their potential applications in molecular design for material science and nanotechnology.