What is the Difference Between Tetrahedral and Octahedral Voids?

Tetrahedral and octahedral voids are gaps in the arrangement of atoms in a crystal structure, specifically in close-packed structures. They are interstitial sites, which are vacancies in the crystal structure that can be occupied by atoms or molecules. Here are the main differences between tetrahedral and octahedral voids:

Tetrahedral Voids:

1. Found in substances with a tetrahedral crystal arrangement.
2. Surrounded by four spheres, forming a triangular shape.
3. Occur on the sides of the unit cell.
4. Coordination number is 4.
5. For a atom with a radius R, the radius of the tetrahedral void is 0.225R.
6. The number of tetrahedral voids for a given number of atoms (N) is 2N.

Octahedral Voids:

1. Found in substances with an octahedral crystal arrangement.
2. Formed by the combination of two tetrahedral voids from different layers, surrounded by six spheres, forming a hexagonal shape.
3. Occur in the center of the unit cell.
4. Coordination number is 6.
5. For a atom with a radius R, the radius of the octahedral void is 0.414R.
6. The number of octahedral voids for a given number of atoms (N) is N.

In summary, tetrahedral and octahedral voids differ in their location, coordination number, and the arrangement of spheres surrounding them. Tetrahedral voids are triangular and found on the sides of the unit cell, while octahedral voids are hexagonal and found at the center of the unit cell.

Comparative Table: Tetrahedral vs Octahedral Voids

Here is a table comparing tetrahedral and octahedral voids:

Tetrahedral voids are triangular-shaped gaps in the crystal structure, surrounded by four spheres, and can be found at the sides of the unit cell. Octahedral voids, on the other hand, are a combination of two tetrahedral voids from two different layers and are located at the center of the unit cell. The radius ratio for tetrahedral voids is 0.225, while for octahedral voids, it is 0.414.