The charge transfer and ion formation in liquid Li-Tl alloys

The 7Li NMR Knight shift, K, and the spin-lattice relaxation time, T1, were measured for liquid Li-Tl alloys. The K decreases rapidly with the addition of Tl up to 20 at.% Tl. In the concentration from 20 to 50 at.% Tl, the K decreases only slightly and the K of 50 at.% Tl is 60% of K for the pure liquid Li. Such a decrease of K is considered as an indication for the strong charge transfer from Li to Tl. These tendencies are similar to those from previous studies for liquid Li-Ga and Li-In alloys. However, beyond 50 at.% Tl, the K increases and reaches to an almost constant value (70% of K for the pure liquid Li). Such a back donation of charge is absent for liquid Li-Ga and Li-In alloys. It is considered that the tendency of the formation of ionic structural unit for liquid Li-Tl alloys is slightly weaker compared with the cases of liquid Li-Ga and Li-In alloys. The T1 is also discussed with the relation to the Knight shift and the electronic properties.