Structure of diopside, enstatite, and magnesium aluminosilicate glasses: a joint approach using neutron and x-ray diffraction and solid-state NMR.
MOHAMMADI, Hesameddin; SILVA, Rita Mendes da; ZEIDLER, Anita; GAMMOND, Lawrence V. D.; GEHLHAAR, Florian; OLIVEIRA JUNIOR, Marcos de; DAMASCENO, Hugo; ECKERT, Hellmut; YOUNGMAN, Randall E.; AITKEN, Bruce G.; FISCHER, Henry E.; FISCHER, Henry E.; KOHLMANN, Holger; CORMIER, Laurent; BENMORE, Chris J.; SALMON, Philip Stephen.
MOHAMMADI, Hesameddin; SILVA, Rita Mendes da; ZEIDLER, Anita; GAMMOND, Lawrence V. D.; GEHLHAAR, Florian; OLIVEIRA JUNIOR, Marcos de; DAMASCENO, Hugo; ECKERT, Hellmut; YOUNGMAN, Randall E.; AITKEN, Bruce G.; FISCHER, Henry E.; FISCHER, Henry E.; KOHLMANN, Holger; CORMIER, Laurent; BENMORE, Chris J.; SALMON, Philip Stephen.
Abstract: Neutron diffraction with magnesium isotope substitution, high energy x-ray diffraction, and 29Si, 27Al, and 25Mg solid-state nuclear magnetic resonance (NMR) spectroscopy were used to measure the structure of glassy diopside (CaMgSi2O6), enstatite (MgSiO3), and four (MgO)x(Al2O3)y(SiO2)1-x-y glasses, with x = 0.375 or 0.25 along the 50 mol. % silica tie-line (1-x -y = 0.5) or with x = 0.3 or 0.2 along the 60 mol. % silica tie-line (1- x - y = 0.6). The bound coherent neutron scattering length of the isotope 25Mg was remeasured, and the value of 3.720(12) fm was obtained from a Rietveld refinement of the powder diffraction patterns measured for crystalline 25MgO. The diffraction results for the glasses show a broad asymmetric distribution of Mg-O nearest-neighbors with a coordination number of 4.40(4) and 4.46(4) for the diopside and enstatite glasses, respectively. As magnesia is replaced by alumina along a tie-line with 50 or 60 mol. % silica, the Mg-O coordination number increases with the weighted bond distance as less Mg2+ ions adopt a network-modifying role and more of these ions adopt a predominantly charge-compensating role. 25Mg magic angle spinning (MAS) NMR results could not resolve the different coordination environments of Mg2+ under the employed field strength (14.1 T) and spinning rate (20 kHz). The results emphasize the power of neutron diffraction with isotope substitution to provide unambiguous site-specific information on the coordination environment of magnesium in disordered materials.
@article={003110101,author = {MOHAMMADI, Hesameddin; SILVA, Rita Mendes da; ZEIDLER, Anita; GAMMOND, Lawrence V. D.; GEHLHAAR, Florian; OLIVEIRA JUNIOR, Marcos de; DAMASCENO, Hugo; ECKERT, Hellmut; YOUNGMAN, Randall E.; AITKEN, Bruce G.; FISCHER, Henry E.; FISCHER, Henry E.; KOHLMANN, Holger; CORMIER, Laurent; BENMORE, Chris J.; SALMON, Philip Stephen.},title={Structure of diopside, enstatite, and magnesium aluminosilicate glasses: a joint approach using neutron and x-ray diffraction and solid-state NMR},journal={Journal of Chemical Physics},note={v. 157, n. 21, p. 214503-1-214503-22},year={2022}}