Molecular QTAIM Topology Is Sensitive to Relativistic Corrections

The topology of the molecular electron density of benzene dithiol gold cluster complex Au4−S−C6H4−S′−Au′4 changed when relativistic corrections were made and the structure was close to a minimum of the Born–Oppenheimer energy surface. Specifically, new bond paths between hydrogen atoms on the benzene ring and gold atoms appeared, indicating that there is a favorable interaction between these atoms at the relativistic level. This is consistent with the observation that gold becomes a better electron acceptor when relativistic corrections are applied. In addition to relativistic effects, here, we establish the sensitivity of molecular topology to basis sets and convergence thresholds for geometry optimization. Quantum theory of atoms in molecules (QTAIM) topology of benzene dithiol gold cluster at the zero‐order regular approximation unrestricted level of theory is reported. Considering a gold cluster complex as a case study, the sensitivity of molecular topology to various physical phenomena is demonstrated. Specifically, new bond paths between hydrogen and gold atoms appeared upon the inclusion of relativistic effects.