Combined Solid-State NMR and Molecular Dynamics Study of the Structure of Strontiuln-Aluminosilicate glasses

International audienceSolid-statc NMR has firmly established itself as a method of choice for provinding key information for the elucidation of glass atomic-scale structure. Recently, a methodology based on the combination of DFT-NMR calculations with molecular dynamics simulations has emerged as a significant step for the improvement of the detailed interpretation of experimental NMR spectra. Using this approach, we have investigated the structure of aluminosilicate Si02-AI203-SrO based glass compositions which are largely unexplored systems.Glasses on the compensation line Al2O3 = SrO. were studied with 170, 29Si and 27Al solid state NMR at high (11.7 T) and very-high (20.0 T) magnetic fields, together with neutron diffraction spectroscopy. Classical and ab-initio molecular dynamics (MD) simulations were perfomed and combined with calculations of NMR parameters with the DFT-GIPAW rnethod. Computed NMR parameters were linked to local structural features to establish relationships between experimental NMR spectra and the underlying topological disorder (in terms of chemical and geometrical disorder) . NMR fingerprints of debated units such astricoordinated oxygen atoms could be predicted with the aims to assess their existence from experimental data. In agreement with experimental NMR data, MD simulations predict that aluminium is predominently tetrahedrally coordinated for all the studied compositions with a small fraction of AlO5 units ranging from 2-5%. Variations of the 29Si NMR spectra, and to a less extent of 27Al spectra, could be quantitatively correlated to the Al/Si mixing. In parallel, the AI/Si connectivities were investigated using