Lattice thermal conductivity of defected tungsten evaluated by equilibrium molecular dynamics simulation

Abstract

Exposed to high fluxes of helium particles and heat, tungsten divertor plates will suffer various forms of damage thus degrading its performance such as its thermal conductivity. In this paper, the equilibrium molecular dynamics method is employed to evaluate the lattice thermal conductivity (LTC) changes of the tungsten lattice containing one type of defects (dislocation loops, helium bubbles and impurity helium atoms). It is found that the LTC of tungsten is slightly reduced in the presence of dilute dislocation loops and vacuum bubbles, while a remarked reduction of the thermal conductivity is engendered by dilute helium particles. A tiny number of helium atoms as randomly-distributed tetrahedral interstitials (accounting for 0.2 % of the total number of atoms in the simulation cell), result in a drastic drop of the LTC to 15 % of that of the perfect tungsten lattice. The phonon density of states of the perfect and defected tungsten lattices are compared to identify the causes of the LTC reduction at the atomic level.