Body-centered tetragonal

Definition

Body-centered tetragonal (BCT) is a type of crystal lattice structure characterized by a tetragonal unit cell that has atoms located at each corner of the cell and an additional atom positioned at the center of the cell. This structure is one of the 14 Bravais lattices, playing a crucial role in determining the properties of materials such as metals and alloys. The body-centered arrangement allows for unique packing efficiencies and influences the mechanical properties of substances that crystallize in this form.

5 Must Know Facts For Your Next Test

1. In a body-centered tetragonal lattice, there are two different lattice parameters: 'a' for the base dimensions and 'c' for the height, where 'a' is equal in both lateral dimensions and 'c' differs, making it distinct from other cubic structures.
2. The body-centered tetragonal structure often occurs in metals such as tantalum and tungsten at certain temperature ranges, affecting their ductility and strength.
3. This type of lattice has a coordination number of 8 for atoms located at the corners and 8 for the atom at the center, leading to unique chemical bonding properties.
4. BCT can be transformed into other structures, such as face-centered cubic (FCC) or body-centered cubic (BCC), depending on temperature and pressure conditions.
5. The unique packing arrangement in BCT lattices allows for high densities in materials, making them desirable for various industrial applications.

Review Questions

• How does the body-centered tetragonal lattice structure influence the mechanical properties of metals that crystallize in this form?
  • The body-centered tetragonal lattice structure affects the mechanical properties of metals by providing a specific arrangement of atoms that influences both strength and ductility. The presence of an atom in the center of the unit cell allows for more efficient packing compared to simple cubic structures, which can enhance the material's resistance to deformation. Additionally, the unique coordination number associated with BCT can lead to variations in how metals respond to stress and strain.
• Compare and contrast the body-centered tetragonal lattice with other Bravais lattices in terms of atomic arrangement and density.
  • The body-centered tetragonal lattice differs from other Bravais lattices like face-centered cubic (FCC) or body-centered cubic (BCC) primarily due to its distinct atomic arrangement, where an atom is located at the center of the unit cell. While BCT maintains a lower symmetry compared to FCC, it provides higher packing efficiency than simple cubic lattices. In terms of density, BCT can offer advantages due to its packing configuration, which typically results in higher material densities compared to FCC or BCC structures under similar conditions.
• Evaluate how temperature and pressure can influence the stability of a body-centered tetragonal structure and its potential transformation into other crystal forms.
  • Temperature and pressure play significant roles in determining the stability of a body-centered tetragonal structure by affecting atomic vibrations and interactions within the lattice. As temperature increases, atoms may gain energy, which can lead to phase transitions where BCT transforms into more stable forms such as face-centered cubic (FCC) or body-centered cubic (BCC). Similarly, changes in pressure can alter interatomic distances and energy states, making it possible for materials to switch between different crystallographic forms based on external conditions.

Related terms

Tetragonal lattice: A type of crystal lattice characterized by two equal axes in one direction and a different length along the third axis, resulting in a rectangular prism shape.

Bravais lattices: A classification system for crystal lattices based on their geometric arrangement, consisting of 14 distinct types that describe how atoms are organized in space.

Coordination number: The number of nearest neighbors surrounding an atom in a crystal lattice, which affects the stability and properties of the material.