Code dependence of calculated crystalline electron densities. Possible lessons for quantum crystallography

Area of Science:

• Crystallography
• Quantum Chemistry
• Materials Science

Background:

• Quantum crystallography integrates electronic structure theory with crystallographic data analysis.
• Theoretically derived electron density (ρ) is crucial for X-ray diffraction refinement and accessing new experimental observables.
• Current quantum crystallography practices may overlook the influence of computational code on derived electron density.

Purpose of the Study:

• To investigate the impact of different computational codes on theoretically derived electron density (ρ) in quantum crystallography.
• To highlight the previously unaddressed factor of computational code selection in quantum crystallography.
• To provide a recommendation for improving the reliability of quantum crystallography studies.

Main Methods:

• Utilizing standard electronic structure codes to compute electron density (ρ).
• Comparing ρ values obtained from different computational codes under various conditions.
• Analyzing the convergence of ρ as a function of computational parameters and code choice.

Main Results:

• Theoretically derived electron density (ρ) is demonstrably dependent on the specific computational code employed.
• Computational conditions alone do not fully determine the resulting electron density.
• Variations in ρ across different codes suggest a significant, underappreciated source of error.

Conclusions:

• The choice of computational code is a critical factor influencing theoretically derived electron density in quantum crystallography.
• Researchers must carefully assess the convergence and consistency of electron density calculations across different software.
• Implementing code-specific convergence checks is essential for robust and reproducible quantum crystallography studies.