title: Polyhedral units and network connectivity in calcium aluminosilicate glasses from high-energy X-Ray diffraction
abstract: Structure factors for Ca (x/2)Al xSi 1-xO (2) glasses (x = 0,0.25,0. 5,0.67) extended to a wave vector of magnitude Q = 40 A (-1) have been obtained by high-energy x-ray diffraction. For the first time, it is possible to resolve the contributions of Si-O, Al-O, and Ca-O coordination polyhedra to the experimental atomic pair distribution functions. It has been found that the connectivity of Si/Al-O tetrahedral network decreases with increasing x due to the emerging of nonbridging oxygens located on Si-O tetrahedra. Calcium maintains a rather uniform coordination sphere for all values of x and so it plays a certain role in determining the glass structure.
authors.affiliation: Department of Physics and Astronomy and Center for Fundamental Materials Research, Michigan State University, East Lansing, Michigan 48823, USA.
authors.initials: V
authors.lastname: Petkov
authors.initials: SJ
authors.lastname: Billinge
authors.initials: SD
authors.lastname: Shastri
authors.initials: B
authors.lastname: Himmel