Comparative studies of compressibility between nanocrystalline and bulk nickel

The authors conducted a comparative study of compressibility between nanocrystalline and bulk nickel using synchrotron x-ray diffraction at pressures up to 7.4 GPa. Their results present a clear evidence of elastic softening in nanocrystalline Ni as compared with the bulk nickel. It is also observed that the bulk moduli determined using the apparent lattice parameters are 17%-18% lower at the smaller diffraction vectors (Q=2 pi/d) than those at the larger Q values. These findings support the results of molecular dynamics simulation and a generalized model of a nanocrystal with expanded surface layer. (c) 2007 American Institute of Physics.