Performance of 3D-space-based atoms-in-molecules methods for electronic delocalization aromaticity indices

Area of Science:

• Quantum Chemistry
• Theoretical Chemistry
• Computational Chemistry

Background:

• Accurate calculation of electronic properties like electron sharing indices (ESI) is crucial for understanding molecular behavior.
• Aromaticity is a key concept in chemistry, influencing molecular stability and reactivity.
• Different theoretical models exist for defining atoms within molecules and calculating their properties.

Purpose of the Study:

• To compare different definitions of atoms in a molecule (AIM) for calculating electron sharing indices (ESI).
• To evaluate the impact of these AIM definitions on electronic aromaticity measures, including I(ring) and multicenter indices (MCI).
• To assess the performance of iterative Hirshfeld, classical Hirshfeld, and Bader's quantum theory of atoms in molecules (QTAIM) schemes.

Main Methods:

• Calculation of ESI and aromaticity indices using fuzzy and disjoint AIM domains.
• Application of iterative Hirshfeld, classical Hirshfeld, and QTAIM methods.
• Analysis of cyclic planar aromatic and nonaromatic molecules of varying ring sizes.

Main Results:

• ESI values for bonded atoms show excellent agreement across all methods, particularly for C-C bonds.
• Significant deviations in ESI are observed for nonbonded interactions between fuzzy and QTAIM schemes.
• Discrepancies in ESI lead to notable differences in aromaticity indices, with disjoint domains yielding more chemically expected trends.

Conclusions:

• The choice of AIM definition significantly influences calculated aromaticity indices.
• Disjoint AIM domains appear more reliable for consistently capturing expected chemical trends in aromaticity.
• Understanding the impact of AIM definitions is essential for accurate theoretical chemistry predictions.