Electron Momentum Distribution Around Vacancy Cluster …
451
Fig. 1 X-ray diffraction spectra of synthesized samples
using the Debye–Scherrer equation (Cullity 1956) and they varied from 9 to 22 nm.
Table 1 shows the crystallite size and their lattice constant.
It is seen from Table 1 that as particle size increases, lattice constant also increases.
The decrease in lattice constant with decreasing particle size can result from strain
induced by the increasing number of surface atoms (i.e., the atoms less surrounded
by neighbor atoms) in an effort to minimize the surface free energy. Unlike in a bulk
solid or coarse crystallite where the number of core atoms far outnumber the surface
atoms and offer stiff resistance to surface reduction, the inner core of a nanoparticle
is soft enough to contract in order to facilitate the minimization of surface energy.
Table 1 The crystallite size, lattice constant, and concentration of CdCl 2
Crystallite size (nm)
Lattice constant ( ˙
A)
Concentration of CdCl 2 (M)
9
4.7986
0.10
17.5
4.8012
0.15
22.0
4.8052
0.20