Janus icosahedral particles: amorphization driven by three-dimensional atomic misfit and edge dislocation compensation

Abstract

Icosahedral nanoparticles composed of fivefold twinned tetrahedra have broad applications. The strain relief mechanism and angular deficiency in icosahedral multiply twinned particlesare poorly understood in three dimensions. Here, we resolved the three-dimensional atomic structures of Janus icosahedral nanoparticles using atomic resolution electron tomography. A geometrically fivefold face consistently corresponds to a less ordered face like two hemispheres. We quantify rich structural variety of icosahedra including bond orientation order, bond length, strain tensor; and packing efficiency, atom number, solid angle of each tetrahedron. These structural characteristics exhibit two-sided distribution. Edge dislocations near the axial atoms and small disordered domains fill the angular deficiency. Our findings provide new insights how the fivefold symmetry can be compensated and the geometrically-necessary internal strains relived in multiply twinned particles.

Three-dimensional atomic interface between metal and oxide in Zr-ZrO2 nanoparticles

“…These observations indicate that when semi-coherent interface forms, a significant amount of strain could occur due to lattice and/or angular mismatch during oxidation. Once the strain caused by bending or twisting is too large, some of the semi-coherent interfaces could possibly turn to disordered structures through amorphization 46 , where the coherency of interface is completely broken. In this direction, the oxide shows the (002) plane.…”