Ionisation of atoms determined by kappa refinement against 3D electron diffraction data.

Area of Science:

• Crystallography
• Materials Science
• Computational Chemistry

Background:

• Conventional 3D electron diffraction (3D ED) structure refinement relies on the Independent Atom Model (IAM), which assumes spherical atoms and neglects bonding effects.
• IAM can lead to inaccurate or biased crystal structure models by not accounting for electron density distribution and charge transfer between atoms.

Purpose of the Study:

• To introduce and validate a refinement strategy beyond the IAM for 3D ED data.
• To demonstrate the capability of kappa refinement to model charge transfers and atomic ionization.
• To improve the accuracy of crystal structure determination from 3D ED data.

Main Methods:

• Application of kappa refinement, an advanced method that models charge transfer while maintaining a spherical atomic model.
• Analysis of five diverse inorganic crystalline samples: quartz, natrolite, borane, lutetium aluminum garnet, and cesium lead bromide.
• Validation of results using periodic Density Functional Theory (DFT) calculations.

Main Results:

• Kappa refinement yielded improved crystal structure models compared to conventional IAM refinements.
• The method successfully provided insights into the ionization states of atoms within the analyzed samples.
• The extracted charge density information offers a more nuanced understanding of chemical bonding.

Conclusions:

• Kappa refinement represents a significant advancement over IAM for 3D ED data analysis.
• This technique enables the extraction of valuable charge density information, leading to more accurate and reliable crystal structures.
• The findings pave the way for more precise structural characterization in materials science and chemistry.