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Distinguish between (i) Hexagonal and monoclinic unit cells (ii) Face-centred and end-centred unit cells. |
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Answer» SOLUTION :(i) In hexagonal unit CELLS, two sides are equal and the two angles are perpendicular and third angle is `120^@`. i.e., `a = b ne c, alpha = BETA = 90^@, gamma = 120^@`. In monoclinic unit cells, the edges are unequal and two angles are right angle. `a ne b nec, alpha = gamma = 90^@, B ne 90^@`. (ii) In face-centred unit cell, the lattice points are located at corners as well as at the centre of every face. While in end-centred unit cell, the lattice points are at corners as well as centre of two alternate faces. The NUMBER of atoms per unit cell in FCC are 4 while in end-centred there are two atoms per unit cell. |
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