Figure (19.5) Reflections from NaCl and kcl crystals (Powder diffractions)
In KCl, K + and Cl - have similar scattering factors and hence there are greater number of absences in KCl.
From X - ray diffraction, we get F h k l for different hkl planes. Since the origin of F h k l is the electron density (r) of different atoms [ Eq (19.3) and Eq (19.8)] it is possible to obtain
(r) from all the F h k l values through
V (r) =
Fh k l e - 2 i ( h x + k y + l z )
(19.16)
where V is the volume of the unit cell and the summation is over all h k l values. This is a very crucial result, since the location of all the atoms in the unit cell (through the values of (r) corresponding to these atoms) can be obtained by using the above equation.
(r) of different atoms [ Eq (19.3) and Eq (19.8)] it is possible to obtain
F
