Simulation study of effects of grain boundary and helium bubble on lattice thermal resistance of tungsten

Abstract

Tungsten (W) as plasma facing material (PFM) has been used in ITER divertor. Many experiments indicate that due to helium (He) ion irradiation the thermal conductivities (TCs) of W can be significantly reduced. In this work, the lattice thermal transport property is studied based on the non-equilibrium molecular dynamics (NEMD) method. Firstly, the Kapitza resistance of grain boundaries (GBs) in W is obtained. It can be confirmed that the Kapitza resistance is positively correlated with GB energies, which reflect the lattice distortion degree in a sense. The result indicates that the distortion energy may play a key role in the thermal properties. Further simulation is performed to study the thermal resistance of GBs with nano He bubble. When the number of He atoms in bubble is less than a value, the thermal resistances are stable and change little. It implies that the effect of GBs is more significant than He bubble to block phonons diffusion. With the number of He atoms increasing, the property of heat conduction deteriorates further because the coupling of He bubble and GBs change the lattice distortion degree.