XAFS studies of alkaline-earth borate glasses

The local structure obtained from calcium K-edge XAFS experiments in CaO-B2 O3 glasses is described. The average coordination number of oxygen around C a2+ ions and the mean distance for Ca-O are found to be approximately 6 and 2.40 similar to 2.41 Angstrom, respectively. The Ca2+ ions have a disorder ed octahedral geometry and a strong preference to reside in vicinity of neg atively charged non-bridging and bridging oxygen in the large cages of the B-O network structure. The XAFS results are in good agreement with MD simul ation results.