First principles modeling on radiation defects in W and W-based alloys

Suzudo, Tomoaki   ; Tsuru, Tomohito   

Rhenium (Re) and Osmium (Os) are produced from W through nuclear transmutation, and they would naturally be solute elements of W crystals under neutron irradiation. In such alloys, stable solvent-solute mixed dumbbells appear because the SIA and Re and Os substitutional atoms are attractive. Using the first-principles methods, we analyzed the atomistic migration patterns of these two transmuted elements and indicated that the mixed dumbbells composed of Re (or Os) and W atoms occasionally become separated, and the Re (or Os) atom jumps to the neighboring site forming another mixed dumbbell. Because the rotation of these mixed dumbbells is easy, these solute elements can be carried for long distance by iteration of jumping and rotation events.