An alloy of metals M and N, crystallises in ccp. Atoms of N occupy lattice points and atoms of M occupy one-third of tetrahedral voids. What is the composition of the unit cell?

Explanation

To determine the composition of the unit cell of the alloy of metals M and N, we can follow these steps:

### Step 1: Understand the structure
The alloy crystallizes in a cubic close-packed (ccp) structure. In a ccp unit cell, there are lattice points at the corners and the face centers.

### Step 2: Calculate the number of atoms of N
In a ccp structure, the total number of atoms (Z) per unit cell can be calculated as follows:
- There are 8 corner atoms, each contributing \( \frac{1}{8} \) to the unit cell:
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