Simulated TEM Imaging of a Heavily Irradiated Metal

Abstract

We recast the Howie-Whelan equations for generating simulated transmission electron microscope(TEM) images, replacing the dependence on local atomic displacements with atomic positions only.This allows very rapid computation of simulated TEM images for arbitrarily complex atomisticconfigurations of lattice defects and dislocations in the dynamical two beam approximation. Large scalemassively-overlapping cascade simulations performed with molecular dynamics, are used togenerate representative high-dose nanoscale irradiation damage in tungsten at room temperature,and we compare the simulated TEM images to experimental TEM images with similar irradiationand imaging conditions. The simulated TEM shows ‘white-dot’ damage in weak-beam dark-fieldimaging conditions, in line with our experimental observations and as expected from previous studies,and in bright-field conditions a dislocation network is observed. In this work we can also comparethe images to the nanoscale lattice defects in the original atomic structures, and find that at highdose the white spots are not only created by small dislocation loops, but rather arise from nanoscalefluctuations in strains around curved sections of dislocation lines.

Keywords: TEM, radiation damage, cascade simulation, radiation induced defects