The algorithm for finding crystalline regions relies on the assumption that the neighbors of a particle in a crystal lattice are arranged in a particular orientation about the particle, and that this orientation of neighbors is the same for nearby particles. The bond order parameter q6(i) of particle i is based on the spherical harmonics (Ylm) and is a measure for the orientation of its neighbors around it. Two adjacent particles with similar orientation of their neighbors have similar bond order parameters and are therefore said to be joined by a crystal-like 'bond'. Particles with 8 or more crystal-like 'bonds' are defined as 'crystal-like'.