New insights in quantum chemical topology studies using numerical grid-based analyses

Area of Science:

• Quantum Chemistry
• Computational Chemistry
• Materials Science

Background:

• Quantum Chemical Topology (QCT) analyzes electron density.
• Existing methods for QCT can be complex and require detailed wave function information.

Purpose of the Study:

• To adapt a grid-based algorithm for analyzing the topology of various one-electron density functions.
• To demonstrate the algorithm's utility beyond charge density decomposition, including the Laplacian of electron density, electron localization function (ELF), and molecular electrostatic potential (MEP).
• To present an implementation (TopChem) and discuss its performance and accuracy.

Main Methods:

• Utilized a recent grid-based algorithm initially designed for electron density decomposition.
• Applied the algorithm to analyze scalar functions including the Laplacian of electron density, ELF, and MEP.
• Developed a program (TopChem) for numerical assignment of grid data points to basin volumes.
• Performed density functional theory (DFT) calculations using Gaussian and plane-wave bases.

Main Results:

• The grid-based algorithm successfully analyzes the topology of ELF and the Laplacian of electron density.
• The algorithm is effective for molecular electrostatic potential (MEP) analysis, a complex and less-studied area.
• TopChem demonstrates robustness and accuracy, with discussed CPU requirements.
• Analysis was performed on individual molecules and crystalline solids.

Conclusions:

• The presented algorithm offers a robust and versatile tool for quantum chemical topology analysis.
• It simplifies the analysis of complex scalar functions, requiring only function values, not wave function details.
• The TopChem implementation provides valuable insights into the electronic structure of molecules and solids, particularly for MEP analysis.