Crystallisation requires particles — atoms, ions, or molecules — to be locked into a repeating three-dimensional pattern. Whether that pattern forms, and how rigid it becomes, depends on two properties of the bonding between the particles: bond strength, which sets how much energy is needed to build or break the lattice, and bond directionality, which sets whether bonds point in specific directions and therefore constrain the geometry of the arrangement.
How Chemical Bonds Drive Crystallisation and Crystal Growth