Size Dependence of Cubic to Trigonal Structural Distortion in Silver Micro- and Nanocrystals under High Pressure

Silver micro- and nanocrystals with sizes of similar to 2-3.5 mu m and similar to 50-100 nm were uniaxially compressed under nonhydrostatic pressures (strong deviatoric stress) up to similar to 30 GPa at room temperature in a symmetric diamond-anvil cell and studied in situ using angle-dispersive synchrotron X-ray diffraction. A cubic to trigonal structural distortion along a 3-fold rotational axis was discovered by careful and comprehensive analysis of the apparent lattice parameter and full width at half-maximum, which are strongly dependent upon the Miller index and crystal size.