What is the Difference Between Crystals and Quasicrystals

The key difference between crystals and quasicrystals is that crystals have an ordered structure that is periodic, whereas quasicrystals also have an ordered structure that is not strictly periodic.

The terms crystals and quasicrystals are useful in the field of crystallography that falls under industrial chemistry. Crystals are the monomeric units of crystalline materials, while quasicrystals are types of crystals that contain arrays of atoms that are in an ordered manner but are not strictly periodic.

CONTENTS

1. Overview and Key Difference
2. What are Crystals 
3. What are Quasicrystals
4. Similarities – Crystals and Quasicrystals
5. Crystals vs Quasicrystals in Tabular Form
6. Summary – Crystals vs Quasicrystals

What are Crystals?

Crystals are the monomeric units of crystalline materials. These solid crystalline compounds contain their atoms, molecules or ions arranged in a highly ordered microscopic structure. These units make up the crystal lattice of the crystalline material. The crystal lattice can extend in all directions. Additionally, we can identify microscopic single crystals of crystalline materials using geometrical shapes.  When considering geometric shapes, the crystals consist of flat faces that have specific and characteristic orientations. Moreover, the field of studying crystals is crystallography. We call the process of formation of crystals crystal growth or crystallization.

In the crystal structure, the atoms, molecules, or ions are arranged in a periodic arrangement. However, all solids are not crystals. There can be non-crystalline substances, as shown in the above image. If we consider water when water starts to freeze, the phase of matter changes from liquid to solid and small ice crystals tend to grow until the fusion occurs (which forms a polycrystalline structure).

We can show a unit cell for crystalline material. The unit cell is an imaginary box that contains one or more atoms in a specific arrangement. Typically, the unit cells tend to stack in a 3D arrangement, forming a crystal. We can recognize the crystals from their shape according to the faces having sharp angles.

Crystallization is the process from which crystals are formed from a fluid or dissolved materials in a fluid. The field of crystallization is very wide because a single fluid is able to solidify into many different forms depending on conditions. Therefore, it is a complex and extensively studied field.

What are Quasicrystals?

Quasicrystals are a type of crystals that contains arrays of atoms that are in an ordered manner but are not strictly periodic. Therefore, quasicrystals may have some similarities with normal crystals. Similarities between the normal crystals and quasicrystals are shown below.

Typically, this type of crystal is well-known for its ability to show five-fold symmetry. This symmetry is impossible in normal periodic crystals. Therefore, the International Union of Crystallography has redefined “crystals” to include details about quasicrystals.

The discovery of quasicrystals took place in 1982. The formation of these crystals is a rare thing because only about 100 known solids tend to form quasicrystals among the 400,000 normal periodic crystals forms known until 2004. Moreover, Dan Shechtman received the Nobel prize for the discovery of quasicrystals.

What are the Similarities Between Crystals and Quasicrystals?

1. Crystals and quasicrystals are types of crystalline material.
2. They display a discrete pattern in X-ray diffraction.
3. Both are able to form shapes with smooth and flat faces.

What is the Difference Between Crystals and Quasicrystals?

The terms crystals and quasicrystals are useful in the field of crystallography. There are differences between them as well as some similarities between these terms. The key difference between crystals and quasicrystals is that crystals have an ordered structure that is periodic as well, whereas quasicrystals also have an ordered structure that is not strictly periodic.

The below infographic lists the differences between crystals and quasicrystals in tabular form for side by side comparison.

Summary – Crystals vs Quasicrystals

Quasicrystals are a type of crystals. They are different from ordinary crystals according to their chemical structure. The key difference between crystals and quasicrystals is that crystals have an ordered structure that is periodic as well, whereas quasicrystals also have an ordered structure that is not strictly periodic.

Reference:

1. “What Is a Crystal? – International Gem Society – IGS.” International Gem Society, 2 July 2021.

Image Courtesy:

1. “Crystalline polycrystalline amorphous2” By Cristal_ou_amorphe.svg: CdangEverything else: Sbyrnes321 – Cristal ou amorphe.svgCrystalline polycrystalline amorphous.svg (CC BY-SA 3.0) via Commons Wikimedia
2. “Ho-Mg-ZnQuasicrystal” By AMES lab., US Department of Energy – (Public Domain) via Commons Wikimedia