Thermodynamic Modeling of Glass Formation and DFT Calculations of Li ₂ O–K ₂ O–SiO ₂ Melt Crystallization Within a Unified Structural Model

This work presents the results of modeling the three-component Li₂O-K₂O-SiO₂ oxide system during cooling from 1250 °C under two different conditions. Calculations were performed for the content of structural units formed during glass formation and for the structure of substances resulting from crystallization of a multialkali silicate melt containing equal amounts of lithium and potassium. The structure was predicted using thermodynamic modeling approaches for glasses and first-principles calculations for crystalline samples. The results of glass structure modeling for compositions 16.5Li₂O-16.5K₂O-67SiO₂, 20Li₂O-20K₂O-60SiO₂ and 25Li₂O-25K₂O-50SiO₂ were shown to be consistent with Raman spectroscopy data. The crystalline phases in annealed samples of the same compositions were identified using X-ray diffraction (XRD), while the possible coexistence regions of stable phases in this system were evaluated using DFT calculations. A good qualitative agreement was demonstrated between the experimental results and theoretical calculations to confirm the crystallization of SiO₂, KLiSi₂O₅, Li₂SiO_3, K₂SiO₃ and KLi₃SiO₄ phases in the system. The results of this work validated the selected computational approaches for modeling glass formation and crystallization of the oxide multialkali melt.