On the stability and mobility of di-vacancies in tungsten

摘要

Properties of small vacancy clusters in tungsten were studied with first-principles calculations. The binding and formation energies of the vacancy clusters increase with the cluster size. Dynamic characteristics of a di-vacancy were specified between room temperature and 700 K with lattice kinetic Monte Carlo calculations, which were parametrised with the present first-principles results for the dissociation barriers. An Arrhenius fit for the di-vacancy diffusion yielded D = 0.04 exp(-1.65 eV kT~(-1)) cm~2 s~( -1)and for the mean lifetime, τ = 0.093 exp( 1.7 eV) kT~(-1) ps. The di-vacancy system was found to be stable up to 500K, due to the high energy needed for its dissociation. Having a carbon impurity was found to increase the tungsten di-vacancy binding energy.