Diffraction study of calcium aluminate glasses and melts: I. High energy x-ray and neutron diffraction on glasses around the eutectic composition

A series of four (CaO)x(Al2O3)(1−x) glasses over the narrow compositional range x = 57.1–66.7 have been studied using high energy x-ray and neutron diffraction. The coordination number of oxygen around aluminum was determined as 4 at all compositions. The coordination number of oxygen around calcium was extracted using a first-order difference method and found to be in the range of 5.2–5.5 up to a distance of 2.75 A for all compositions, with the possibility of additional correlations at higher distances. The results are in good agreement with two recent molecular dynamics simulations and confirm an asymmetric distribution of CaO correlations in the glass structure.