Environments of Mg and Al in MgO–Al2O3–SiO2 glasses: A study coupling neutron and X-ray diffraction and Reverse Monte Carlo modeling

The structure of six glass compositions in the MgO–Al2O3–SiO2 system was investigated using neutron and X-ray diffraction. Reverse Monte Carlo modeling was used to reproduce experimental structure factors derived from diffraction experiments. The environment of Mg was determined and corresponds to an average of 5.1 ± 0.1 oxygens at a mean distance of 2.00 ± 0.02 Å with little change as the compositions vary. Tetrahedral, pentahedral and octahedral polyhedra are found with a majority of MgO5. The Al environment reveals the presence of high-coordinated Al in agreement with 27Al Nuclear Magnetic Resonance results. The Reverse Monte Carlo models were used to interpret the structural role of Mg and Al. The [5]Al species show a trend to be localized in the same regions, which have important implications to quantify the Si/Al ordering in aluminosilicate glasses and melts.