University of Saskatchewan
Department of Geological Sciences
Local structure (A) and electron density (B) of the E’1 center in quartz calculated from the tri-vacancy model with an Al atom at a neighboring Si site. Note the presence of a peroxy linkage ( = 1.48 Ǻ) and that the AlO4 group has an elongated Al-O1 bond of 1.91 Ǻ. Contours are at intervals of 0.005 e/bohr3 and from -0.01 to 0.415 e/bohr3.
Trace defects in minerals exert profound impacts on material properties such as colour, density, rheology, stability, electrical and thermal conductivity, magnetism, seismic velocity, and many more.
Electron paramagnetic resonance (EPR) spectroscopy has been and continues to be the technique of choice for quantitative studies of paramagnetic defects in minerals and other materials, because of its unparallelled sensitivity for detection and structural study of dilute defects. However, a combination of factors such as the complexity of natural materials like minerals, existence of magnetically similar defects, and lack of other complementary experimental techniques with similar sensitivities, makes the EPR data often difficult to interpret.
Yuanming Pan, a Professor of Geology at the University of Saskatchewan, is harnessing WestGrid and Compute Canada - Calcul Canada’s advanced computing resources to run first-principles theoretical models as an approach for studying the structures and properties of defects in minerals.
“This research would not be possible without WestGrid and Compute Canada - Calcul Canada infrastructure because our first-principles calculations using the supercell approach are extremely demanding in computing resources,” says Pan.
The calculations Pan is running on WestGrid’s systems are being used to predict the geometries, electronic structures, magnetic properties and stability of paramagnetic defects. An example of recent theoretical calculations is the new tri-vacancy model for the E’1 center in α-quartz (SiO2), which reproduces all 29Si hyperfine and superhyperfine coupling constants determined by EPR experiments and explains its common association with the [AlO4]0 center in this mineral (Li and Pan, 2012).
The results uncovered by Pan’s theoretical calculations stand to complement EPR experimental data and have a wide range of applications, including geochemical modeling, geochronology, remediation of heavy metalloid contamination, nuclear waste disposal, and mineral exploration.