DFT Studies of HfO2-Na2O-SiO2 glasses

Reference Presenter Authors
10-019 Peter Kroll Kroll, P.(UT Arlington); Using density functional calculations we study hafnia-soda-silica (HfO2-Na2O-SiO2) glasses. Models with up to 10 mol% HfO2 in Na2O·2SiO2 and Na2O·3SiO2 are generated via a melt-quench procedure by ab-initio molecular dynamic (aiMD) simulations. 29Si-NMR chemical shifts are subsequently computed within the gauge-including projector augmented wave (GIPAW) method. Additional annealing sequences using aiMD are performed to receive low-energy models, which provide insight into the thermochemistry of the HfO2-Na2O-SiO2 system. We find a negative enthalpy of mixing for adding HfO2 to Na2O·3SiO2, and our value agrees well with calorimetric experiments. While we predict a positive enthalpy of mixing HfO2 into Na2O·2SiO2, the solubility of hafnia in that glass turns out to be large. Addition of HfO2 to the soda-silicate glass increases elastic constants and hardness. 29Si- chemical shifts are related to different environments of O, and correlation function we derive allow for better interpretation of experimental data.
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