Hexagonal System

Definition

The hexagonal system is one of the seven crystal systems characterized by a unit cell with a hexagonal shape, defined by three equal axes in the same plane at 120-degree angles, and a vertical axis of a different length. This unique geometry influences the physical properties and symmetry of crystals, making it an essential part of understanding crystal structures, lattice types, and Bravais lattices, as well as their implications for directional properties in materials.

5 Must Know Facts For Your Next Test

1. In the hexagonal system, the three axes in the base plane are equal in length and intersect at 120 degrees, while the vertical axis can differ in length.
2. The symmetry of hexagonal crystals can be described by a six-fold rotational axis and three vertical mirror planes.
3. Common minerals that crystallize in the hexagonal system include quartz, beryl, and graphite, showcasing diverse physical properties.
4. The hexagonal system is significant for its unique directional properties which can affect material behavior, especially in anisotropic materials.
5. Hexagonal close packing (HCP) is a common arrangement for atoms in metallic crystals, which has implications for material density and stability.

Review Questions

• How does the geometric configuration of the hexagonal system influence its crystallographic properties?
  • The geometric configuration of the hexagonal system, with its three equal axes at 120 degrees and a differing vertical axis, results in unique symmetry and anisotropic properties. This configuration allows for specific directional behaviors in materials that can be exploited in various applications. Understanding these geometric features helps predict how materials will respond to stress, heat, and other physical influences.
• Discuss the significance of the hexagonal system in relation to Bravais lattices and how it fits into crystallography.
  • The hexagonal system represents one of the key types within the classification of Bravais lattices. It is essential for categorizing crystal structures based on their symmetry and spatial arrangements. The distinct properties of hexagonal lattices allow for better predictions regarding material behavior, making it a crucial component in fields like material science and solid-state physics.
• Evaluate how knowledge of crystallographic directions and zone axes is impacted by understanding the characteristics of the hexagonal system.
  • Understanding the characteristics of the hexagonal system enhances knowledge about crystallographic directions and zone axes by providing insight into how crystal symmetry affects these orientations. For example, Miller indices used to describe planes in hexagonal crystals reveal how atomic arrangements align along specific directions. This evaluation not only aids in predicting material properties but also informs practical applications in manufacturing processes where directionality plays a critical role.

Related terms

Unit Cell:

The smallest repeating unit in a crystal lattice that reflects the overall symmetry and structure of the entire crystal.

Bravais Lattice:

A classification of distinct lattice types based on the arrangement of points in space, with the hexagonal system being one of the 14 possible types.

Miller Indices:

A notation system in crystallography that describes the orientation of planes and directions in a crystal lattice, crucial for understanding crystallographic directions and zone axes.