Validation

This page records a comparison against a DFT-PBE0 melt-quench reference for amorphous Ga₂O₃. It compares random placement followed by CHGNet relaxation, the hybrid workflow (--hybrid-ensemble, stages 4–7), and the full melt-quench workflow with CHGNet on GPU.

The reported ensembles contain N = 20 structures each. The repository includes the comparison figure and one representative structure, but not the full ensembles or the complete run configurations and seeds. The commands below show how to run a similar comparison; they do not reproduce these numerical results exactly.

Note

The reported coordination and bond-angle analysis uses --cutoff auto-rdf, the analysis default since v1.0.0rc2. It estimates each bond cutoff from the first minimum of the partial RDF and falls back to a radii-based value when no suitable minimum is found. The alternative --cutoff auto uses minimum-separation estimates and can truncate broad first shells. Inspect the RDF and selected cutoff when comparing coordination numbers between studies. Changes to cutoff detection can also change reanalysed results; see Changelog.

a-Ga₂O₃

System: Ga₁₆₀O₂₄₀ supercell (400 atoms), N=20 structures per ensemble

Reference: DFT-PBE0 melt-quench ensemble from Kaewmeechai, Strand & Shluger, Phys. Rev. B 111, 035203 (2025)

Workflow: Four ensembles compared, DFT-PBE0 (PRB 2025), AmorphGen Random + CHGNet relax, AmorphGen Hybrid (Stages 4-7), AmorphGen Full MQ (Stages 1-7, NPT throughout).

a-Ga₂O₃ structure (Ga: dark, O: red)

Results vs DFT-PBE0 + experiment

Metric	DFT-PBE0	Random	Hybrid	Full MQ	Experiment
Density (g/cm³)	4.83	4.63	4.70	4.37	4.78–4.84
Ga–O bond (Å)	1.895	1.925	1.922	1.913	—
Ga–O coordination	4.42	4.38	4.42	4.33	~4.5 (EXAFS)
O–Ga–O angle (°)	107.5	107.7	107.6	107.9	—

Note

In this comparison, the local structural averages are close to the PBE0 reference across all three AmorphGen workflows. Density agreement varies: the Full MQ ensemble is about 9% less dense than the PBE0 ensemble. The guide examples use NVT for hybrid MD and NPT for full MQ, so their volume constraints differ. Density differences depend on both the potential and the simulation protocol.

Validation figure

Panels: (a) partial RDFs (Ga–O solid, Ga–Ga dashed, O–O dotted); (b) coordination distributions (Ga-centred top half, O-centred bottom); (c) bond-angle distributions (O–Ga–O solid, Ga–O–Ga dashed); (d) per-structure density compared with PBE0 reference and experimental range. Blue = DFT-PBE0 reference, orange = AmorphGen Random, green = AmorphGen Hybrid, pink = AmorphGen Full MQ.

Run a similar comparison

Run from a repository checkout after installing CHGNet. Save the example configurations from Hybrid workflow and MQ-ensemble workflow as hybrid.yaml and mq.yaml, and provide your own Ga2O3_supercell.xyz for the full MQ option. Review the temperatures, durations, and cell constraints for your system before running.

# 1. Generate and relax 20 random structures (Ga160O240, 400 atoms)
amorphgen --random-gen \
    --composition "Ga2O3*80" \
    --n-structures 20 \
    --relax --model chgnet --device cuda --cell-filter none \
    --work-dir random_ga2o3/

# 2. Run either Hybrid or Full MQ workflow

#   Option A - Hybrid (from the random placements, Stages 4-7)
amorphgen --hybrid-ensemble \
    --input-dir random_ga2o3/random_initial/ \
    --config hybrid.yaml \
    --work-dir hybrid_ga2o3/

#   Option B - Full melt-quench from a crystal supercell
amorphgen Ga2O3_supercell.xyz \
    --mq-ensemble --n-structures 20 \
    --config mq.yaml \
    --work-dir mq_ga2o3/

# 3. Analyse against the bundled reference YAML (mq_ga2o3/final/ for Option B)
amorphgen --analyse \
    --input-dir hybrid_ga2o3/final/ \
    --reference examples/reference_a_Ga2O3.yaml \
    --save-report report.txt --save-plot plots/ --save-pdf

Both ensemble modes collect their final structures in <work-dir>/final/. Analyse random_ga2o3/random_opt/ for the random-plus-relaxation comparison. Use amorphgen.analysis.compare_ensembles to plot the ensembles together; see Structure analysis.

Reference files for a-SiO₂, a-GeO₂, a-HfO₂ and a-IrO₂ sit next to it in examples/ in the repository. The reference file examples/reference_a_Ga2O3.yaml contains literature ranges for automatic match/concern/fail scoring. These example files are not installed by the Python wheel.

Data availability

A representative a-Ga₂O₃ structure is included in the repository at examples/validation/ga2o3/example_final.xyz. The full 20-structure ensembles are not included. To inspect the bundled structure:

amorphgen --analyse examples/validation/ga2o3/example_final.xyz \
    --reference examples/reference_a_Ga2O3.yaml

Its individual metrics need not equal the ensemble averages in the table.

Reference data sources

• a-Ga₂O₃: Kaewmeechai, Strand & Shluger, Phys. Rev. B 111 (2025) 035203 (DFT-PBE0 ensemble); Stehlik et al., J. Non-Cryst. Solids 458 (2017) 14 (neutron + EXAFS); Yoshioka et al., J. Phys. Condens. Matter 19 (2007) 346211 (DFT-MD).