Institute of High Pressure Physics

This archive contains data derived from density functional theory (DFT) calculations performed using the SIESTA package. The study focuses on predicting the migration behavior of point defects at In_xGa_1−xN/GaN heterointerfaces (𝑥=0.125,0.25). The heterostructures were modeled as superlattices, with the growth direction aligned along the hexagonal 𝑐-axis. The GaN substrate was represented using a 4×4 lateral unit cell with six double Ga-N monolayers, while the InGaN layers consisted of six double Ga(In)-N mixed monolayers strained to the lattice constant of GaN. Indium dopant atoms were systematically placed in lattice sites within the InGaN layers to achieve compositions of In_0.125Ga_0.875N and In_0.25Ga_0.75N. Each superlattice model comprised 384 atoms.

The archive includes results on the diffusion of neutral and charged defects, such as nitrogen vacancies (𝑉_𝑁), gallium vacancies (𝑉_𝐺𝑎), indium vacancies (𝑉_𝐼𝑛), and complexes of indium substitutional atoms with nitrogen vacancies (𝐼𝑛_𝐺𝑎𝑉_𝑁).

Defect migration energy barriers were calculated using the Nudged Elastic Band (NEB) method, employing 12 intermediate "images" to represent atomic configurations along migration paths.

Structure of the Archive

The archive contains two main categories based on the material composition: In_0.125Ga_0.875N_GaN and In_0.25Ga_0.75N_GaN. Each category includes subdirectories for various interface and defect configurations.

Defect Configurations:

Subdirectories such as VN_q=0, and others represent systems with defects like nitrogen vacancies (V_N) in specific charge states (q=0, q=3+, or q=3-).

Each defect directory includes subfolders (c_{x}{Material}_{y}{Material} or a_{z}_{Material}), where {x}, {y}, and {z} specify the layer number relative to the interface, and {Material} identifies the type (e.g., GaN or InGaN) monolayer.

For example: c_1GaN_1InGaN , meaning defect migrate in c-direction from 1st GaN layer to 1st InGaN layer 

The files include:

DFT_energy.txt: Total energy results.

MEP.txt: Minimum energy path calculations for atomic migration.

image_#.xsf: Snapshots along the reaction pathways.

DFT_pressure.txt: file contains detailed information about the pressure in the system as a function of the defect type, charge state, and its specific placement within a particular monolayer.

Data Usage

Relaxed Geometries: Found in structure.xsf files, they describe the final atomic positions after relaxation.

Energy Comparisons: DFT_energy.txt files allow comparison of relative total energies across configurations to identify the most stable structures.

Migration Pathways: MEP.txt files provide insights into the energetics of atom migration or defect transformations.

Units and File Format

Energy is reported in electron-volts (eV), length in Angstroms (Å), and pressure in kilo Bar (kBar).