Structure in liquid KTl investigated by means of neutron diffraction using ²⁰⁵Tl isotope substitution

In recent neutron diffraction measurements on liquid KTl, a prepeak was observed in the structure factor at a rather low value of the wave vector of 8 nm^-1. It corresponds to a periodicity in real space of 0.93 nm. In solid KTl and K₈Tl₁₁, Tl clusters of, respectively, 6 and 11 atoms occur. It was concluded that parts of these clusters survive in the liquid state. In order to obtain more information on the structure of the clusters, we have performed an additional neutron diffraction experiment on D4 (ILL, Grenoble France) using ²⁰⁵Tl isotope substitution. From the additional data it is concluded that the prepeak occurs only in the Tl-Tl partial structure factor. Using RMC modelling of the isotopic data we are able to determine partial structure factors. The average Tl-Tl coordination number is 4.0 ± 0.1.