Rings

rings(structure, max_size) finds the primitive (shortest-path) rings of Franzblau on the periodic bond graph. A cycle with a shortcut through the graph is a sum of smaller rings, so it is not primitive. ring_counts aggregates by size, ring_membership counts rings per atom and is_aromatic is a labelled heuristic (five- or six-membered, all C/N/O) until bond orders and planarity are available. rings_explicit and ring_counts_explicit use only the stored explicit bonds, which is the census a builder states: distance perception is not allowed to add a close contact across a pore.

rust

use xtalforge::core::rings;

for ring in rings(&structure, 8)? {
    println!("{} atoms:", ring.size());
    for step in &ring.path {
        println!("  atom {} image {:?}", step.atom, step.image);
    }
}

Ring { atoms, path } carries both forms: atoms is the sorted set of unique P1 indices for membership tests, and path is the ring in walking order as RingStep { atom, image }. Add image to the atom's fractional position to lay the path out in Cartesian space; a small cell can therefore show the same atom more than once, and size() is the path length. ring_paths returns only the paths.

The search is periodic-aware because the graph is built on the P1 cell and the cycle walk carries lattice images. Results are sorted deterministically, and the same structure and limit return the same list on every surface.

See Primitive rings for the walk, the Franzblau filter, the path budget and the golden-corpus validation.

Rings ​

Rings