Unit cell in rutile

To determine the dimensions of the unit cell of TiO, (rutile) and to calculate (sin 6)/A for reflections from the (111) and (301) planes. 

Rutile is tetragonal and the imit cell is denoted by a, a, c). When examined with Rh Ka radiation of wave-length X = 0.614 A, the lowest-order Bragg reflection from the (100) face of the crjrstal occurs at a Bragg angle 0 = 7°44. The lowest-order reflection from the (001) face occurs at 0 = 11°57 (Vegard, Phil. Mag. 1916, 32, 65). 

Both the above-mentioned reflections are second-order since the first-order reflections are absent on account of the crystal symmetry (compare problem 23). 

For the second-order reflection from the (100) face this becomes 

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