In a multi layered close-packed structure:a)There are twice as many te...
Ans.
No. of octahedral holes No. of close packed atoms
No. of Tetrahedral holes No. of close packed atoms
Hence, in a multi-layered close-packed structure, there are twice as many tetrahedral holes as many close-packed atoms.
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In a multi layered close-packed structure:a)There are twice as many te...
Close-packed structures
Close-packed structures, also known as densest packing arrangements, are three-dimensional arrangements of atoms or spheres in which the maximum number of particles occupy the smallest possible space. Two common close-packed structures are the face-centered cubic (FCC) and hexagonal close-packed (HCP) structures.
Tetrahedral and Octahedral Holes
In a close-packed structure, there are voids or holes between the packed atoms. These voids can be classified into two types: tetrahedral holes and octahedral holes.
- Tetrahedral holes: These are smaller voids that can accommodate four atoms or spheres in a tetrahedral arrangement. These holes are formed by the triangular arrangement of three atoms in one layer and the atom directly above in the next layer.
- Octahedral holes: These are larger voids that can accommodate six atoms or spheres in an octahedral arrangement. These holes are formed by the arrangement of three atoms in one layer and three atoms in the layer above, creating an octahedral shape.
Number of Tetrahedral and Octahedral Holes
To determine the number of tetrahedral and octahedral holes in a close-packed structure, we need to consider the arrangement of atoms in the structure.
- In an FCC structure, there are 4 atoms per unit cell. Each atom is surrounded by 12 nearest neighbors, forming an octahedral arrangement. Therefore, the number of octahedral holes is equal to the number of atoms in the structure, which is 4 per unit cell. On the other hand, each atom is also part of 8 tetrahedral holes. Since there are 4 atoms per unit cell, the total number of tetrahedral holes is 4 x 8 = 32 per unit cell. Hence, option 'A' is correct.
- In an HCP structure, there are 6 atoms per unit cell. Each atom is surrounded by 12 nearest neighbors, forming an octahedral arrangement. Therefore, the number of octahedral holes is equal to the number of atoms in the structure, which is 6 per unit cell. Similarly, each atom is also part of 6 tetrahedral holes. Since there are 6 atoms per unit cell, the total number of tetrahedral holes is 6 x 6 = 36 per unit cell.
In summary, in a multi-layered close-packed structure, there are twice as many tetrahedral holes as there are close-packed atoms. This is because each atom is part of 8 tetrahedral holes in an FCC structure and 6 tetrahedral holes in an HCP structure.