Mesoscale thermodynamic analysis of atomic-scale dislocation–obstacle interactions simulated by molecular dynamics

Abstract

Given the time and length scales in molecular dynamics (MD) simulations of dislocation–defect interactions, quantitative MD results cannot be used directly in larger scale simulations or compared directly with experiment. A method to extract fundamental quantities from MD simulations is proposed here. The first quantity is a critical stress defined to characterise the obstacle resistance. This mesoscopic parameter, rather than the obstacle ‘strength’ designed for a point obstacle, is to be used for an obstacle of finite size. At finite temperature, our analyses of MD simulations allow the activation energy to be determined as a function of temperature. The results confirm the proportionality between activation energy and temperature that is frequently observed by experiment. By coupling the data for the activation energy and the critical stress as functions of temperature, we show how the activation energy can be deduced at a given value of the critical stress.

Keywords:

• atomistic simulation
• dislocation dynamics
• dislocation interactions
• dislocation theory
• irradiation effects
• thermal activation of deformation

Acknowledgements

This work was partially supported by the Division of Materials Sciences and Engineering and the Office of Basic Energy Sciences, US Department of Energy, under contract with UT-Battelle, LLC. It was also supported by the European project PERFECT (FI60-CT-2003-208840 and by grant GR/S81162/01 from the UK Engineering and Physical Sciences Research Council.