Why Bond Critical Points Are Not "Bond" Critical Points

Area of Science:

• Quantum Chemistry
• Theoretical Chemistry
• Computational Chemistry

Background:

• The topological analysis of electron densities, using the Quantum Theory of Atoms in Molecules (QTAIM), identifies critical points (CPs).
• A common practice has been to equate (3,-1) CPs, often termed "bond" CPs (BCPs), with chemical bonds.
• This interpretation, originating from the late 1970s and early 1980s, has led to significant confusion in recent years.

Purpose of the Study:

• To critically review recent computational studies on molecular electron densities.
• To demonstrate why (3,-1) CPs are not universally equivalent to chemical bonds.
• To propose a change in terminology to prevent misinterpretation of QTAIM data.

Main Methods:

• Review of recent computational studies on molecular electron densities.
• Topological analysis of electron densities.
• Analysis of the properties of (3,-1) critical points.

Main Results:

• Recent computational studies cast serious doubt on the universal equivalence between (3,-1) CPs and chemical bonds.
• The term "bond" critical point (BCP) is misleading and contributes to confusion.
• (3,-1) CPs do not universally indicate the presence of a chemical bond.

Conclusions:

• The terminology of (3,-1) CPs should be changed from "bond" critical points (BCPs) to "line" critical points (LCPs).
• This proposed terminology detaches topological properties from a priori chemical interpretations.
• Adopting the term LCPs will help prevent further misinterpretation of QTAIM results.