An energy-conserving two-temperature model of radiation damage In single-component and binary Lennard-Jones crystals

摘要

Two-temperature models are used to represent the interaction between atoms and free electronsduring thermal transients such as radiation damage, laser heating, and cascade simulations. In thispaper, we introduce an energy-conserving version of an inhomogeneous finite reservoirtwo-temperature model using a Langevin thermostat to communicate energy between the electronicand atomic subsystems.This energy-conserving modification allows the inhomogeneoustwo-temperature model to be used for longer and larger simulations and simulations of small energyphenomena, without introducing nonphysical energy fluctuations that may affect simulation results.We test this model on the annealing of Frenkel defects. We find that Frenkel defect annealing islargely indifferent to the electronic subsystem, unless the electronic subsystem is very tightlycoupled to the atomic subsystem.We also consider radiation damage due to local deposition of heatin two idealized systems.We first consider radiation damage in a large face-centered-cubicLennard-Jones.(LJ)single-component crystal that readily recrystallizes. Second, we considerradiation damage in a large binary glass-forming LJ crystal that retains permanent damage. We findthat the electronic subsystem parameters can influence the way heat is transported through thesystem and have a significant impact on the number of defects after the heat deposition event. Wealso find that the two idealized systems have different responses to the electronic subsystem. Thesingle-component Li system anneals most rapidly with an intermediate electron-ion coupling and ahigh electronic thermal conductivity. If sufficiently damaged, the binary glass-forming LI systemretains the least permanent damage with both a high electron-ion coupling and a high electronicthermal conductivity. In general, we find that the presence of an electronic gas can affect short andlong term material annealing.