Atomic-scale insight of size-dependent compressibility of nanocrystalline Pt under high pressure

Abstract

Size-dependent compressibility of nanocrystalline (nc)-Pt under high hydrostatic pressure is investigated by the atomic method. The correlations between the size dependence, grain boundary thickness, and lattice distortion effects are also reported. A nc-Pt model containing glue-like grain boundaries and crystalline grains with different grain sizes is built in molecular dynamics (MD) simulations, compatible with the diamond anvil cell-x ray diffraction measurements. The MD simulations demonstrate that with the grain size decreasing, the bulk modulus of nc-Pt increases until the grain size reaches a critical value of 16–17 nm and then decreases. Crystal cores with the critical size of 16 nm tend to shrink, while those with a bigger or smaller grain size exhibit an expansion behavior instead. Such transition of the lattice distortion is also dependent on the grain boundary thickness. These observations provide the atomic mechanistic interpretation for the size-dependent compressibility of nanocrystalline.