How do quasicrystals differ from amorphous solids such as glass?

Quasicrystals and amorphous solids, such as glass, differ fundamentally in their atomic arrangement and structural order.

While amorphous solids lack long-range order, quasicrystals possess it. In amorphous materials, atoms are arranged without a repeating pattern or consistent orientation over long distances, resulting in diffuse rings in electron diffraction patterns. Conversely, quasicrystals exhibit a highly ordered, deterministic structure that allows for sharp Bragg diffraction peaks, similar to ordinary crystals.123

The primary distinction lies in the nature of that order:
* Amorphous Solids: Characterized by the absence of long-range order, these materials may possess short-range order (the arrangement of immediate neighbors), but atomic positions become uncorrelated at greater distances.2
* Quasicrystals: These materials feature quasiperiodic translational order. Unlike ordinary crystals, which have a repeating unit cell, quasicrystals are formed from structures that do not recur at regular intervals. They often display rotational symmetries—such as fivefold symmetry—that are mathematically forbidden in periodic crystals.341

In essence, quasicrystals represent a unique state of matter that bridges the gap between the total disorder of amorphous solids and the strict, periodic regularity of conventional crystals.4