Q.The total number of particles in a body centred cubic [bcc] unit cell is

Counting atoms per unit cell using the corner (1/8 share) and body-centre (full share) contribution rules gives a 1:1 ratio, so the formula is AB.

In a body-centred cubic (bcc) unit cell:

• Corner atoms: 8 corners x 1/8 share each = 1 atom of A per unit cell. …

A body-centred cubic (bcc) unit cell has atoms at the 8 corners and 1 at the body centre; counting each corner atom's fractional share and adding the centre atom gives 2 atoms per unit cell.

In a bcc arrangement, atoms occupy two kinds of positions:

1. CORNER ATOMS: There are 8 atoms, one at each corner of the cube. Each corner atom is shared among 8 adjacent unit cells, so only 1/8 of each corner atom effectively belongs to a single unit cell.

Contribution from corners = 8 x (1/8) = 1 atom.

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