Interaction potentials for modelling GaN precipitation and solid state polymorphism.

Area of Science:

• Materials Science
• Computational Chemistry
• Solid State Physics

Background:

• Existing gallium nitride (GaN) force fields are limited, modeling either bulk crystals or isolated ions.
• A unified model is needed to simulate GaN aggregate formation and crystal growth processes.

Purpose of the Study:

• To develop a versatile molecular mechanics model for GaN interactions across various scales.
• To enable simulations of GaN aggregate formation and crystal growth.

Main Methods:

• Utilized formal +3 and -3 charges for gallium and nitride ions, respectively.
• Incorporated additional potential energy terms to account for charge transfer in GaN crystals.
• Fitted and benchmarked the model against experimental data for wurtzite, zinc-blende, and rock-salt polymorphs.

Main Results:

• Achieved reasonable agreement with quantum chemical references and experimental data for GaN aggregate structures and formation energies.
• Accurately predicted elastic properties of bulk GaN crystals and the wurtzite to rock-salt transformation pressure.
• Demonstrated the transferability of the force field for modeling GaN nanoparticles using simulated annealing.

Conclusions:

• The developed molecular mechanics model provides a unified approach for simulating GaN systems from small complexes to bulk materials.
• This model facilitates the study of complex phenomena like aggregate formation and crystal growth in GaN.
• The model's accuracy and transferability are validated against experimental and quantum chemical data.