Oxygen-17 nuclear magnetic resonance study of the structure of mixed cation calcium-sodium silicate glasses at high pressure: implications for molecular link to element partitioning between silicate liquids and crystals.
The structure of silicate glasses and the corresponding liquids at high pressure and their structure-property relations remain difficult questions in modern physical chemistry, geochemistry, and condensed matter physics. Here we report high- resolution solid-state O-17 3QMAS NMR spectra for mixed cation Ca-Na silicate glasses quenched from melts at high pressure up to 8 GPa. The spectra provide the experimental evidence for the varying pressure-dependence in two different types of nonbridging oxygen (NBO) environments (i.e., Na-O-Si and mixed (Ca,Na)-O-Si) in the single glass composition. The percentage of NBO drops significantly with increasing pressure and is a complex function of melt composition, including cation field strength of network modifying cations. A decrease in NBO fraction with pressure is negatively correlated with the element partitioning coefficient between crystals and liquids at high pressure.
Lee
Sung Keun
SK
School of Earth and Environmental Sciences, Seoul National University, Seoul, Korea. sungklee@snu.ac.kr
Cody
George D
GD
Fei
Yingwei
Y
Mysen
Bjorn O
BO