Analytical and computational modeling of fluctuation electron microscopy from a nanocrystal/amorphous composite

Area of Science:

• Materials Science
• Condensed Matter Physics
• Electron Microscopy

Background:

• Nanocrystal/amorphous composites serve as models for medium-range order in amorphous materials.
• Fluctuation electron microscopy (FEM) is a key technique for probing these structures.

Purpose of the Study:

• To analytically and computationally investigate the FEM signal from nanocrystal/amorphous composite models.
• To refine existing models by incorporating partial occupancy, deviation parameter effects, and size distributions.
• To analyze the impact of kinematic vs. dynamical scattering and internal disorder/strain on FEM variance.

Main Methods:

• Analytical modeling of nanocrystal/amorphous composites, extending previous work.
• Computer simulations using both kinematic and dynamical scattering approximations.
• Investigation of disorder and strain effects within nanocrystals.

Main Results:

• The improved analytical model eliminates the artificial maximum in FEM signal versus nanocrystal volume fraction.
• Dynamical scattering calculations yield variance approximately 15% lower than kinematic scattering.
• Nanocrystal disorder significantly reduces variance, especially at longer scattering vectors.

Conclusions:

• The refined models provide a more accurate representation of FEM signals in amorphous materials.
• Understanding the influence of scattering approximations and internal structural variations is critical for interpreting FEM data.
• This work enhances the capability to characterize medium-range order in amorphous systems.