The structure of liquid tin

Abstract

X-ray diffraction patterns have been obtained from liquid tin under good experimental conditions with particular emphasis on obtaining clean, oxide-free surfaces. The patterns show that a considerable degree of structure exists in the melt in contrast with simple liquids such as molten Na, K, Cu and Au. Analysis by a radial distribution method shows that there are two distances of atomic separation in the melt. The first is clearly defined as 3·27 Å. The second is about 2·7 Å, so that the near distance of closest approach of grey tin is re-established in the liquid. The picture of liquid tin which emerges is one of tetrahedra of grey tin floating in a matrix of metallic tin, with possibly, interchange of atoms between the two states. It is not possible to put an exact figure to the relative proportions of atoms in the two states, other than those in the grey tin state, represent between 5 and 20% of the whole.