Medium-range order

Copper in the medium-range order (MRO) regime. This is the first regime where Voronoi grain seeding is introduced: 9 Å grains hold a handful of well-coordinated Cu atoms each, and the random-rotation grain boundaries keep longer-range correlations well short of a full nanocrystal.

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=120,
    grain_size=9.0,
    bond_weight=0.85,
    angle_weight=0.0,
    repulsion_weight=1.3,
    hard_core_scale=0.89,
    nonbond_push_scale=0.72,
    displacement_sigma=0.045,
)

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.