Effect of grain boundary on lattice thermal conduction of tungsten revealed by molecular dynamics simulations

Tungsten (W) and tungsten-based materials are being considered to be used in the divertor and the first wall as plasma facing materials (PFMs) in the fusion reactor, which requires them to withstand the heat loads. The influence of grain boundaries on the heat flux has been studied by the molecular dynamics (MD) simulations in this paper. Various grain boundaries have been constructed in simulation cells and their lattice thermal conductivities (LTCs) and thermal resistances have been calculated. It turns out that there exist sharp temperature drops across these grain boundaries, indicating that the LTCs near grain boundaries are much smaller than those inside the bulk tungsten. The grain boundary effect on the LTCs of polycrystalline W samples has been analyzed by the combination of MD and finite element results. The results may be potentially helpful for the design of the international thermonuclear experimental reactor (ITER) and the choice of PFMs.