Transonic Dislocation Propagation in Diamond

TL;DR

This study provides experimental evidence of transonic dislocation motion in diamond using femtosecond x-ray radiography, revealing dislocations moving faster than the sound speed, which advances understanding of material behavior under extreme conditions.

Contribution

First direct visualization of transonic dislocation motion in diamond, confirming theoretical predictions and expanding knowledge of dislocation dynamics at ultrafast speeds.

Findings

Dislocations in diamond can move transonically.

Stacking faults extend faster than diamond's sound speed.

Ultrafast dislocation motion observed with femtosecond x-ray radiography.

Abstract

The motion of line defects (dislocations) has been studied for over 60 years but the maximum speed at which they can move is unresolved. Recent models and atomistic simulations predict the existence of a limiting velocity of dislocation motions between the transonic and subsonic ranges at which the self-energy of dislocation diverges, though they do not deny the possibility of the transonic dislocations. We use femtosecond x-ray radiography to track ultrafast dislocation motion in shock-compressed single-crystal diamond. By visualizing stacking faults extending faster than the slowest sound wave speed of diamond, we show the evidence of partial dislocations at their leading edge moving transonically. Understanding the upper limit of dislocation mobility in crystals is essential to accurately model, predict, and control the mechanical properties of materials under extreme conditions.