Observation of Transient Structural-Transformation Dynamics in a Cu ₂ S Nanorod

Abstract

The study of first-order structural transformations has been of great interest to scientists in many disciplines. Expectations from phase-transition theory are that the system fluctuates between two equilibrium structures near the transition point and that the region of transition broadens in small crystals. We report the direct observation of structural fluctuations within a single nanocrystal using transmission electron microscopy. We observed trajectories of structural transformations in individual nanocrystals with atomic resolution, which reveal details of the fluctuation dynamics, including nucleation, phase propagation, and pinning of structural domains by defects. Such observations provide crucial insight for the understanding of microscopic pathways of phase transitions.

Surface modification-induced phase transformation of hexagonal close-packed gold square sheets

“…In addition, the electron beam-induced phase transformation has also been observed, such as the transformation of Cu 2 S nanorods from low-chalcocite to highchalcocite structures 14 . Meanwhile, cation exchange has also been used for the structure manipulation of inorganic nanocrystals [15][16][17] .…”

Simulations of nanocrystals under pressure: Combining electronic enthalpy and linear-scaling density-functional theory

“…[10][11][12] Moreover, sufficiently small nanocrystals can be synthesized with few or no defects and are thus ideal models to study the kinetics of solid-solid phase transitions. 13,14 Recently, progress has been made in directly observing structural transformations in nanocrystals 15 and bulk single crystals. 16 Direct monitoring of transformation pathways in nanosystems is, however, a) Electronic mail: niccolo.corsini@imperial.ac.uk still challenging with the resolution of existing experimental probes and understanding can thus greatly benefit from the insights that computer simulations provide.…”

Visualization of nanocrystal breathing modes at extreme strains

“…For example, surface energies play a crucial role in nanoparticle phase stability, leading to size-dependent modifications of solid-liquid 1,2 or solid-solid 3,4 transition temperatures, but the dynamics of these transformations have not been resolved using techniques providing both atomic-scale and femtosecond resolution, the relevant length and timescales for these processes. The elastic properties and stress and strain response exhibited by nanocrystals are size dependent with novel mechanical properties emerging at the nanoscale, associated with variations in bulk moduli and the ability to withstand extreme stresses without inelastic or plastic responses [5][6][7][8][9] .…”