Copper

Copper is a good stress test for tricor. Its face-centred cubic structure (a = 3.615 Å) has twelve-fold close-packed coordination and four distinct first-shell bond angles (60°, 90°, 120°, 180°). The built-in Supercell.PRESETS dictionary is tuned for covalent silicon, so copper is run here with material-specific parameters that keep the angle springs weak and rely on bond + repulsion springs to shape the local environment.

Overview

All six regimes at 40 × 40 × 40 Å, rotating in sync. Drag any panel to orbit manually. The tetrahedral bond filter used in the silicon overview is disabled here because copper’s first shell spans many angles, so bonds are drawn whenever they fall inside the radial tolerance (any of the twelve FCC neighbour distances).

g(r) per regime overlaid on a single axis. The legend identifies each curve by the regime it was measured from:

Reference crystal

from ase.build import bulk
atoms = bulk("Cu", "fcc", a=3.615)

Disorder regimes

Click any regime for the full interactive trajectory viewer and g3 distribution.

• Liquid
• Amorphous
• Short-range order
• Medium-range order
• Long-range order
• Nanocrystalline

Preset summary

Copper-specific parameter dictionaries used throughout this case. Fields left blank use the default (bond_weight=1.0, angle_weight=0.5, repulsion_weight=3.0, hard_core_scale=1.0, nonbond_push_scale=1.0).

Regime	num_steps	grain_size (Å)	bond_weight	angle_weight	repulsion_weight	hard_core_scale	nonbond_push_scale	displacement_sigma
liquid	40	-	0.04	0.00	0.45	0.78	0.38	-
amorphous	100	-	0.35	0.00	0.85	0.88	0.60	-
short-range order	100	7.0	0.6	0.00	1.0	0.88	0.65	0.06
medium-range order	120	9.0	0.85	0.00	1.3	0.89	0.72	0.045
long-range order	140	12.5	1.1	0.00	1.6	0.91	0.82	0.03
nanocrystalline	200	18.0	1.5	0.00	2.0	0.94	0.95	0.01

Angle springs are turned off everywhere (angle_weight=0) because the FCC first-shell angular distribution is multimodal (60°, 90°, 120°, 180°), so a single-target angle spring would fight the natural geometry. Order is built up by progressively stiffer bond and repulsion springs, larger Voronoi grains, and tighter hard_core_scale / nonbond_push_scale instead. bond_weight walks 0.04 → 1.5 across the ladder; nonbond_push_scale walks 0.38 → 0.95 so the effective first-shell radius progressively approaches the reference pair_peak. Liquid + amorphous use no grains; SRO through nanocrystalline grow the Voronoi grain size from 7 Å → 18 Å.