Modelling the lattice dynamics in Si(x)Ge(1-x) alloys

Area of Science:

• Materials Science
• Computational Physics
• Solid-State Chemistry

Background:

• Accurate simulation of thermodynamic and thermal transport properties in random alloys is crucial.
• Simplified models are needed to efficiently predict alloy behavior.

Purpose of the Study:

• To develop and validate a simplified second nearest neighbour model for Si(x)Ge(1-x) alloys.
• To assess the model's ability to capture lattice dynamics and thermal properties.

Main Methods:

• Utilized density functional theory (DFT) to calculate force constant matrices for pure Si, pure Ge, and Si0.5Ge0.5.
• Extracted nearest neighbour contributions directly from DFT.
• Obtained effective interactions for second nearest neighbour contributions.

Main Results:

• The simplified second nearest neighbour model reliably captures the lattice dynamics of Si(x)Ge(1-x) alloys.
• Thermal properties, including the expansion coefficient, were accurately reproduced.
• The model demonstrated transferability to random Si(x)Ge(1-x) alloys.

Conclusions:

• A simple second nearest neighbour model is effective for simulating thermal properties of Si(x)Ge(1-x) alloys.
• The model's parameters derived from DFT ensure reliable predictions.
• This approach provides a computationally efficient method for studying random alloys.