Are "GAPT Charges" Really Just Charges?

Area of Science:

• Computational Chemistry
• Quantum Chemistry
• Molecular Modeling

Background:

• Generalized Atomic Polar Tensor (GAPT) is a widely used charge model in computational chemistry.
• GAPT possesses unique characteristics that differentiate it from standard charge partitioning schemes.
• Existing comparisons of charge models often struggle to directly incorporate GAPT due to its distinct features.

Purpose of the Study:

• To explore the unique features of GAPT, focusing on its dependence on multiple geometries and its dynamic nature.
• To demonstrate a method for extracting static and dynamic components from GAPT using any static charge model.
• To provide a conceptual framework for understanding the correlation between GAPT and Quantum Theory of Atoms in Molecules (QTAIM) charges.

Main Methods:

• Analysis of GAPT's dependence on molecular geometry.
• Development of a procedure to derive static and dynamic parts of GAPT from static charge models.
• Conceptual evaluation comparing GAPT and QTAIM charge models.

Main Results:

• A method is presented to obtain both static and dynamic contributions of GAPT from existing static charge models.
• The strong correlation between GAPT and QTAIM charges is partially explained through a conceptual evaluation.
• Infrared charges, like GAPT, benefit from interpretation as a sum of static charges and dynamic atomic dipoles.

Conclusions:

• GAPT's dynamic character and geometric dependence can be systematically analyzed and decomposed.
• The study provides a unified perspective on GAPT and QTAIM, highlighting their underlying connections.
• An improved interpretation of infrared charges is proposed, emphasizing their dynamic components.