Electron density and thermal motion of diamond at elevated temperatures

Area of Science:

• Crystallography
• Materials Science
• Solid-State Physics

Background:

• Understanding the electron density and thermal motion of materials like diamond is crucial for predicting their properties.
• Previous studies have explored these properties, but high-accuracy data across a wide temperature range is essential for refinement.

Purpose of the Study:

• To precisely determine the electron density and thermal motion of diamond from 100 K to 1000 K.
• To validate theoretical models against experimental data for atomic displacement parameters (ADPs).
• To investigate the temperature dependence of electron density at the bond critical point.

Main Methods:

• Synchrotron powder X-ray diffraction (PXRD) with a high-accuracy detector system.
• Iterative Wilson-Hansen-Coppens-Rietveld procedure to decouple thermal motion and electron density.
• Density functional theory (DFT) for theoretical static structure factors.
• Harmonic phonon calculations (HPC) for comparison with experimental ADPs.

Main Results:

• Experimental determination of diamond's electron density and thermal motion across a wide temperature range.
• Observed harmonic and isotropic thermal motion, with excellent agreement between experimental ADPs and theoretical HPC.
• Experimentally determined Debye temperature (ΘD) of 1883(35) K.
• Electron density properties at the bond critical point remained constant with temperature.

Conclusions:

• The thermal motion of diamond is harmonic and isotropic within the studied temperature range.
• Theoretical models (DFT and HPC) accurately predict experimental results for diamond's thermal motion.
• The crystallographic convolution approximation is valid for diamond up to 1000 K.