Interplanar spacing dhkl

Now envision this lattice of imaginary points in the same space occupied by the crystal. For a small real unit cell, interplanar spacings dhkl are small, and hence the lines from the origin to the reciprocal lattice points are long. Therefore, the reciprocal unit cell is large, and lattice points are widely spaced. On the other hand, if the real unit cell is large, the reciprocal unit cell is small, and reciprocal space is densely populated with reciprocal lattice points. 

X-ray powder-diffraction experiments involve the interpretation of the powder pattern considering the position (Bragg angle 9 or interplanar spacing dhkl)... 

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