# Medium-range order
Medium-range ordered silicon with grains of ~13 Å diameter. Produces 4-5
visible maxima in the radial pair correlation function, with broad peaks
that decrease in amplitude with radius.
## Parameters
```python
from ase.build import bulk
import tricor as tc
atoms = bulk("Si", "diamond", a=5.431)
shell_target = tc.CoordinationShellTarget.from_atoms(atoms, phi_num_bins=90)
cell = tc.Supercell.from_atoms(
atoms,
cell_dim_angstroms=(40, 40, 40),
r_max=10, r_step=0.1, phi_num_bins=90,
rng_seed=42,
)
cell.generate(
shell_target,
num_steps=200,
grain_size=12.0,
bond_weight=2.0,
angle_weight=0.8,
repulsion_weight=2.2,
hard_core_scale=0.93,
nonbond_push_scale=0.75,
displacement_sigma=0.04,
)
```
## Relaxation trajectory
Interactive 3D viewer of the shell-relaxation trajectory (40 × 40 × 40 Å cell).
Drag to rotate, scroll to zoom. Controls below the canvas play, scrub, and change
playback speed.
## g3 distribution
Measured from the **final (post-relaxation) atoms**. The heatmap is the
reduced three-body density in units of the uniform random reference, where white
= 1.0, blue = depleted, red = enhanced. The lower panel shows the pair
profile g(r); the shaded amber band marks the first-neighbour shell used as
the root-bond integration window for the g3 slice. For silicon there is a
single Si-Si-Si triplet channel.