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

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.