Figure 3.

The bulk moduli of nano- and micro-crystalline at the corresponding diffraction vectors Q (Q = 2π/d). The bulk modulus values plotted here are determined based on the “apparent lattice parameters” calculated from individual Bragg reflections. The insert at the lower right is a tentative/generalized model of a Ni nanocrystal with strained (expanded) surface layer [32-34], where R₀ is radius of the core, S₀ the thickness of the surface shell, a₀ interatomic distance in a perfect crystal lattice (in the core) and a_s interatomic distance at the grain surface