Calcium environment in silicate and aluminosilicate glasses probed by (43)Ca MQMAS NMR experiments and MD-GIPAW calculations

(43)Ca MQMAS NMR spectra of three silica-based glasses in which Ca(2+) ions play different structural roles have been collected and processed in order to extract the underlying NMR parameter distributions. The NMR parameters have been interpreted with the help of molecular dynamics simulations and DFT-GIPAW calculations. This synergetic experimental-computational approach has allowed us to investigate the Ca environment, to estimate Ca coordination numbers from MD-derived models, and to push further the discussion about (43)Ca NMR sensitivity to the first and second coordination spheres: (43)Ca δiso and Ca-O distance can be successfully correlated as a function of Ca coordination number.