Why is reciprocal lattice used?
The reciprocal lattice plays a fundamental role in most analytic studies of periodic structures, particularly in the theory of diffraction. In neutron, helium and X-ray diffraction, due to the Laue conditions, the momentum difference between incoming and diffracted X-rays of a crystal is a reciprocal lattice vector.
How is reciprocal lattice constructed in direct lattice?
The reciprocal lattice can be constructed from the real lattice (Fig. 2). The x-axis has dimensions of [1/distance] and lattice spacing is 1/a. The reciprocal lattice points have been indexed as 1, 2, 3, etc., which correspond to (1) , (2), (3) 'planes' (actually points in 1D) in the real space lattice.