Amorphous

Copper in the amorphous regime: random starting positions (no grain seeding) relaxed with weak bond + repulsion springs. The soft repulsion opens up a first-neighbour shell around 2.55 Å without imposing any angular order, giving a broad pair distribution characteristic of a metallic glass. Angle springs stay off so the angular distribution settles into the broad multimodal shape typical of a metallic glass.

Parameters

from ase.build import bulk
import tricor as tc

atoms = bulk("Cu", "fcc", a=3.615)
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=100,
    grain_size=None,
    bond_weight=0.35,
    angle_weight=0.0,
    repulsion_weight=0.85,
    hard_core_scale=0.88,
    nonbond_push_scale=0.60,
)

Angle springs are turned off so the angular distribution is shaped entirely by the competition between bond springs and repulsion. The result is a well-defined first neighbour shell with no medium-range crystallinity - characteristic of a metallic glass.

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.