GRADE Classification
GRADE (General Recognition and Analysis of Diverse Enclosures) classifies the hydrate structure type based on cage composition analysis.
How It Works
GRADE operates in two stages:
- Cage Detection: Runs TRACE internally to enumerate all cage polyhedra
- Structure Classification: Analyzes the ratio of cage types to determine the crystal structure
Structure Types
| Structure | Cage Composition | Unit Cell |
|---|
| sI | 2 x 5^12 + 6 x 5^12·6^2 | Cubic (Pm3n) |
| sII | 16 x 5^12 + 8 x 5^12·6^4 | Cubic (Fd3m) |
| sH | 3 x 5^12 + 2 x 4^3·5^6·6^3 + 1 x 5^12·6^8 | Hexagonal (P6/mmm) |
| Mixed | Combination of multiple structure types | - |
| Amorphous | No dominant structure pattern | - |
Confidence Score
GRADE returns a confidence value between 0 and 1:
| Range | Interpretation |
|---|
| 0.9 - 1.0 | High confidence, clear structure |
| 0.7 - 0.9 | Moderate confidence, mostly one type |
| Below 0.7 | Low confidence, mixed or amorphous |
Running GRADE
- Upload your
.gro file
- Navigate to the ANALYZE tab
- Select GRADE algorithm
- Click RUN GRADE
The result panel will show:
- Structure type (sI, sII, sH, mixed, or amorphous)
- Confidence score
- Cage counts broken down by type
When to Use GRADE
- Use GRADE when you want to quickly identify the structure type of a hydrate sample
- Use TRACE or HTR when you need detailed per-cage analysis or ring-level information
GRADE is ideal for screening large trajectory datasets where you need a quick structure classification for each frame.
Reference
GRADE is based on the classification scheme described in:
Hsu, Y.-C. & Lin, S.-T. (2025). GRADE: General Recognition and Analysis of Diverse Enclosures. The Journal of Physical Chemistry B.
