The structure of erbium doped sodium silicate glasses

The structure of erbium doped sodium silicate glasses 1Er(2)O(3)-xNa(2)O-(99-x)SiO2 (x = 0, 10, 20, 30) were studied by molecular dynamics simulations. The simulated glasses were compared with neutron diffraction and other experimental structural data. Silicon oxygen network ring size distributions and Q(n) distributions, the local structures around erbium ions, including the pair distribution functions, bond angle distributions, coordination number, dipole and quadrupole. moments, were calculated. Their changes with sodium concentration were studied. It was found that both the Er-O bond length and the erbium coordination number increases from silica to sodium silicate glasses. Erbium ions adopt more favorable and uniform coordination environments in sodium silicate glasses. Erbium and sodium distribution and erbium clustering in the glasses were characterized. Erbium clustering is less obvious in sodium silicate glasses than in silica. Bond valences calculations of the simulated glasses provide a useful way to study the simulated glass structure. The comparison of bond valence of simulated glasses with related crystalline materials showed that the biggest difference be on the modifier sites. (c) 2005 Elsevier B.V. All rights reserved.