Short- and Intermediate-Range Order in Liquid Bi–BiBr3 Mixtures: Importance of Voids

Abstract

The neutron diffraction (ND) measurements and the detailed structural modeling by reverse Monte Calro (RMC) simulation have been performed for l-BiBr 3 and l-45 and 55 mol % Bi mixtures. The partial structure factor S i j ( Q ), partial radial distribution function g i j ( r ), and snapshot produced from RMC configurations have been examined. The structure of l-BiBr 3 is dominated by the network of trigonal pyramidal units. The l-mixtures consist of the –Br–Bi–Br– chain fragments terminated by Br. A Voronoi–Delaunay analysis has been applied to characterize the voids within network or chain. We find that the voids are surrounded by six pyramids in l-BiBr 3 and by chains in l-mixture. The packing density is 0.59 for l-BiBr 3 and 0.45 for l-45 mol % Bi mixture which is substantially low compared with that of dense random packing. The void–void structure factor S ' V–V ( Q ) involving void centers have the pre-peak at ∼1.2 A -1 which is in common with the pre-peak in experimentally observed S ( Q ). It is co...