研究目的
To investigate the high-pressure phase transformation of monocrystalline silicon during nanoindentation at cryogenic temperature (1 K) using molecular dynamics simulation, focusing on the force-displacement curve and the corresponding phase transformation.
研究成果
The MD simulation revealed that at cryogenic temperature (1 K), the phase transformation of monocrystalline silicon during nanoindentation is significantly influenced by indenter radius and depth. The absence of pop-out events at higher indentation depths and the appearance of surface extrusion were attributed to the retained DDS outside the indentation, which restricts the transformation of Si-II and causes material extrusion due to residual internal stress. These findings highlight the unique effects of cryogenic temperature on silicon's phase transformation behavior.
研究不足
The study is limited by the use of a virtual indenter and the specific conditions of cryogenic temperature (1 K), which may not fully represent real-world indentation scenarios. The simulation also does not account for all possible environmental variables that could affect phase transformations.
1：Experimental Design and Method Selection:
Molecular dynamics simulation was conducted using LAMMPS to simulate nanoindentation on monocrystalline silicon at 1 K. The simulation employed a virtual hemispherical indenter modeled using a repulsive force. The empirical bond-order potential developed by Erhart and Albe was used for Si atoms interaction.
2：Sample Selection and Data Sources:
A monocrystalline silicon specimen of 30 × 30 × 23 nm containing 1,037,893 atoms was used. The model included boundary, thermostatic, and Newton layers for structural stability and heat dissipation.
3：List of Experimental Equipment and Materials:
Virtual hemispherical indenter with varying radii (3, 4, 5, and 6 nm) and maximum indentation depths (2, 2.5, 3, 3.5, and 4 nm).
4：5, 3, 5, and 4 nm).
Experimental Procedures and Operational Workflow:
4. Experimental Procedures and Operational Workflow: The simulation included loading, holding at maximum depth, and unloading phases. The temperature was kept at 1 K using NVE statistical ensemble after equilibration with NVT.
5：Data Analysis Methods:
The modified coordination number and construct surface mesh (CSM) in OVITO were used to analyze the coordination number of atoms and separate the surface from the interior of the crystal. Different cutoff values were used to distinguish phases.
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