title: Modeling the Structure of Complex Aluminosilicate Glasses: The Effect of Zinc Addition.
abstract: An empirical potential structure refinement of neutron and X-ray diffraction data combined with extended absorption fine structure evidence has been applied to the investigation of two distinct sets of complex aluminosilicate glasses containing different quantities of zinc. Data come from (i) neutron and X-ray total scattering experiments, which have been performed at the ISIS neutron spallation source (SANDALS beamline) and at the European Synchrotron Radiation Facility (ID11 beamline), and (ii) EXAFS experiments which have been performed at the European Synchrotron Radiation Facility (BM23 beamline). By careful examination of the modeled ensemble of atoms, a wide range of structural information has been extracted: coordination numbers, bond distances, cluster sizes, type of oxygen sharing, and the preference of large cations to adopt a charge-compensating role. The first series of glasses, which is characterized by a fixed network modifier element content (i.e., Na), shows how the introduction of Zn at the expense of Si and Al network forming elements does not significantly alter the polymerization degree, as a result of its dominant 4-fold coordination. In the case of the second series, which is characterized by fixed network forming element content (i.e., Si and Al), it is shown how the replacement of a network modifier element (i.e., Ca) with the introduction of Zn does not change the propensity of Zn to be mainly 4-fold coordinated by promoting the network. Where appropriate the experimental results have been compared with classical theoretical approaches such as stoichiometric models based on Zachariasen's rules and computational routines.
authors: ESRF The European Synchrotron, 71 Rue Des Martyrs, Grenoble, France 38000.
authors: Andrea
authors: A
authors: Bernasconi
authors: Dipartimento di Scienze della Terra, Università degli Studi di Milano , Milano, Italy.
authors: Monica
authors: M
authors: Dapiaggi
authors: Dipartimento di Scienze della Terra, Università degli Studi di Milano , Milano, Italy.
authors: Alessandro
authors: A
authors: Pavese
authors: ESRF The European Synchrotron, 71 Rue Des Martyrs, Grenoble, France 38000.
authors: Giovanni
authors: G
authors: Agostini
authors: Maurizio
authors: M
authors: Bernasconi
authors: ISIS Pulsed Neutron and Muon Source, Science and Technology Facilities Council, Rutherford Appleton Laboratory , Harwell Oxford Didcot, OX11 0QX, United Kingdom.
authors: Daniel T
authors: DT
authors: Bowron