Molecular to ionic transition of BiCl3 in LiCl–KCl eutectic melt

The local structures of molten BiCl3 and its mixtures in LiCl–KCl eutectic melt were investigated by X-ray absorption fine structure (XAFS) technique. The first Bi–Cl correlation in molten pure BiCl3 shows covalent nature, since the distance was almost the same as sum of the covalent radii of Bi and Cl and the coordination number was almost 3. The similar property was also observed in the mixture of 75% BiCl3 with LiCl–KCl eutectic melt. Drastic change was detected in 25% BiCl3 mixture melt. The first Bi–Cl distance was the sum of the ionic radii in molten 25% BiCl3 melt. The results suggest that BiCl3 changes from molecular liquid to ionic by mixing with alkali chlorides.