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Neutron diffraction experiments are reported of the equiatomic liquid Zintl alloys NaSn and KPb, over a wide temperature range from 873 to 1873 K. In the crystalline state, these are semiconducting compounds containing tetrahedrally coordinated polyanions (Sn 4 4− , Pb 4 4− ). For liquid KPb, diffraction results indicate the survival of polyanions in the expanded liquid alloy even to the highest temperature measured, as can be inferred from the persistence of the peak of S(Q) at Q ≈ 1 A −1 , which is indicative of intermediate-range order. The position of this peak shifts towards lower Q -values, its height decreases, and its width increases with temperature and correspondingly decreasing density. In liquid NaSn, this so-called prepeak has disappeared at 1873 K. The experimental results are compared with the results of recent ab initio molecular dynamics and computer modelling studies. |
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