Polydisperse sphere packing in one call

build_sphere_system() is the sphere counterpart of build_ga_system(): give it per-particle radii and a target packing fraction, and it returns a minimized State plus a ready-to-step System. Under the hood it draws a loose random configuration via random_sphere_configuration() at initial_phi (default 0.3, or the target phi if that is lower), then quasistatically compresses to phi with FIRE (time step fire_dt).

import jax

jax.config.update("jax_enable_x64", True)  # type: ignore[no-untyped-call]

import numpy as np

from jaxdem.utils.particle_creation import build_sphere_system
from jaxdem.utils.packing_utils import compute_packing_fraction


def summarize(label, state, system):
    phi = float(compute_packing_fraction(state, system))
    box = np.asarray(system.domain.box_size)
    print(f"[{label}]  N={state.N}  phi={phi:.4f}  box={box}")

1. Monodisperse 3D sphere packing, periodic, neighbor_list

state, system = build_sphere_system(
    particle_radii=[0.1] * 64,
    phi=0.55,
    dim=3,
    dt=1e-3,
    collider_type="neighbor_list",
    seed=0,
)
summarize("3D monodisperse, periodic, neighbor_list", state, system)

[3D monodisperse, periodic, neighbor_list]  N=64  phi=0.5500  box=[0.78698894 0.78698894 0.78698894]

2. Bidisperse 2D disk packing, reflect walls, naive collider

state, system = build_sphere_system(
    particle_radii=[0.08] * 40 + [0.12] * 10,
    phi=0.70,
    dim=2,
    dt=1e-3,
    domain_type="reflect",
    collider_type="naive",
    seed=1,
)
summarize("2D bidisperse, reflect, naive", state, system)

[2D bidisperse, reflect, naive]  N=50  phi=0.7000  box=[1.33984917 1.33984917]

3. Short Verlet rollout on the 2D system

for _ in range(100):
    state, system = system.step(state, system)
print("100 Verlet steps on the 2D system completed.")

100 Verlet steps on the 2D system completed.