研究目的
Investigating the atomic structure of nanodiamond and its evolution upon annealing up to 1200°C using real space neutron diffraction analysis supported by molecular dynamics simulations.
研究成果
The atomic structure of nanodiamond grains evolves with annealing, transitioning from truncated octahedrons with (100) and (111) surfaces to octahedrons with only (111)B surfaces at 1200°C. Graphitization occurs predominantly at (111) surfaces, and the methodology combining PDF analysis with MD simulations effectively identifies structural changes and internal strains in nanocrystals.
研究不足
The study is limited to specific nanodiamond samples (UD96) and annealing conditions up to 1200°C. MD simulations use simplified models and the Tersoff potential, which may not capture all atomic interactions accurately. The analysis assumes certain distributions and may not account for all real-world variations in nanodiamond properties.
1：Experimental Design and Method Selection:
The study uses powder diffraction data analyzed by the direct space Pair Distribution Function (PDF) method combined with Molecular Dynamics (MD) simulations. Neutron diffraction data were collected, and PDF analysis was performed to determine lattice strain, crystallite shape, and size distribution. MD simulations used the Tersoff potential to model diamond nanograins.
2：Sample Selection and Data Sources:
Detonation nanodiamond powder UD96 from Microdiamant AG, Switzerland, with 96% diamond phase and mean particle size of 4.5 nm, was used. Samples were annealed in vacuum at 300, 600, 800, 1000, and 1200°C for 2 hours. Neutron diffraction data were collected at the NPDF station at LANSCE, Los Alamos.
3：5 nm, was used. Samples were annealed in vacuum at 300, 600, 800, 1000, and 1200°C for 2 hours. Neutron diffraction data were collected at the NPDF station at LANSCE, Los Alamos.
List of Experimental Equipment and Materials:
3. List of Experimental Equipment and Materials: Nanodiamond powder UD96, vacuum annealing furnace, neutron diffraction setup at NPDF station, software: PDFgetN for data reduction, NanoPDF64 for PDF data elaboration, POLY-classic for MD simulations.
4：Experimental Procedures and Operational Workflow:
Annealing of powder samples, neutron diffraction data collection at room temperature, data reduction to obtain S(Q) and G(r), MD simulations with Tersoff potential for 20ps at 300K, comparison of experimental and theoretical G(r) functions using NanoPDF
5：Data Analysis Methods:
Analysis of G(r) functions to derive apparent lattice parameters, baselines, and differential interatomic distance diagrams δ(r). Statistical comparison with MD models to identify grain size distribution, surface structure, and presence of stacking faults.
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