Mechanical Engineering - Engineering Materials - Discussion
Discussion Forum : Engineering Materials - Section 3 (Q.No. 15)
15.
In a unit cell of close packed hexagonal space lattice, there are twenty four atoms.
Discussion:
16 comments Page 2 of 2.
Sohan said:
7 years ago
[12 c (1/6)] + [2 * 650 (1/2)] + [3 (interior)] = 6.
Jana said:
7 years ago
The hexagonal closest packed (hcp) has a coordination number of 12 and contains 6 atoms per unit cell.
The face-centred cubic (fcc) has a coordination number of 12 and contains 4 atoms per unit cell.
The body-centred cubic (bcc) has a coordination number of 8 and contains 2 atoms per unit cell.
The face-centred cubic (fcc) has a coordination number of 12 and contains 4 atoms per unit cell.
The body-centred cubic (bcc) has a coordination number of 8 and contains 2 atoms per unit cell.
Anu said:
7 years ago
It is 17 atoms.
Ahmed said:
6 years ago
In a unit cell, not some atoms shared with adjacent unit cell/s, then shared atom can't be counted as complete 1 atom.
Like in bcc, atom at the center of the cube completely owned by the unit cell hence its share 1, but atom at the corners of the cube is shared by 7 more adjacent unit cell then its share will be 1/8 and there are 8 such corners, so 1/8 x 8 = 1, hence in bcc has 1 (from centre + 1 (corners) = 2 atoms.
Similarly, HCP has 12 atoms per unit cell.
Like in bcc, atom at the center of the cube completely owned by the unit cell hence its share 1, but atom at the corners of the cube is shared by 7 more adjacent unit cell then its share will be 1/8 and there are 8 such corners, so 1/8 x 8 = 1, hence in bcc has 1 (from centre + 1 (corners) = 2 atoms.
Similarly, HCP has 12 atoms per unit cell.
Ali said:
6 years ago
It is 17 atoms.
Vinay BEL said:
5 years ago
It is 17 atoms.
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