X-ray Diffraction and Molecular Dynamics Study of CdF_2-BdF_2-LiF Glass

Glass forming regions in the CdF2-BaF2-LiF system were determined through melting-quenching technique. The structure of 36CdF2-34BaF2-30LiF (mol%) (CBL glass) was studied by Xray diffraction and molecular dynamics simulation methods. The Cd atoms are six-, seven- and eightfold coordinated by fluorines. The average Cd--F bond length is 2.29A. The Cd--Cd atom distance is about 3.52A for edge-sharing and 4.03A for corner-sharing in the MD-derived glass.The glass structure can be discribed as a network made up of edge--sharing and corner-sharing [CdFn] polyhedra which are partial linked by Li+ ions. Tile role of Li+ ions in the fluoride glasses was discussed. It was proposed that Li+ may play tile outpolarization effort in fluoride glass as it does in the oxide one. This effort can play a positive role to the connectivity of the network based on the good glass formers. However, in the glass based on the weak--bonded glass formers,the relative strong Li--F bond results in a decrease of its chemical durability as it does in the CdF2-BaF2-LiF system.