Abstract High-purity quartz (SiO2 purity99.995%) is a critical basic material supporting the advancement of strategic emerging industries, including photovoltaics and semiconductors. The origin and efficient purification of high-purity quartz have been research hotspots in recent years. In hydrothermal mineralization systems, H+ are key active components in hydrothermal fluids. They have a notable influence on the migration behavior of impurity ions within the quartz lattice and the purification of quartz crystals. However, the specific mechanisms are still unclear. Based on first-principles calculation methods, this study systematically explores the formation energy, charge transfer rules, and regulation mechanism of migration barriers of H+ on characteristic gap impurity ions (Li+, Na+, and K+) within the quartz lattice in a fluid. The study found that H+ significantly changed the bonding state between impurity ions and the SiO2 lattice through charge compensation, reducing the charge transfer between Li+, Na+, K+ and the SiO2 lattice, changing the formation energy from negative to positive, significantly lowering the migration barriers, and effectively promoting the diffusion and migration of these alkali metal ions within the lattice. The crystal structure changes of quartz and the synergistic effect of H+ further optimize the migration process of impurity ions: the channels along the c-axis in α-quartz and β-quartz lattices are the most favorable for impurity migration, while in the tridymite lattice, the channels along the b-axis are the optimal pathways for impurity migration. As the structure changes, the migration barrier of Li+, Na+, and K+ shows a gradual decrease trend. In the lattice of tridymite, the intervention of H+ reduces the maximum migration barriers of the three ions to 0.25, 0.48, and 0.94 eV respectively, achieving the optimal migration efficiency, which is closely related to the differences in lattice structures of different crystal phases. This study reveals the regulation mechanism of the migration of impurity ions in quartz lattice by H+ in hydrothermal fluids at the atomic scale, providing theoretical support for elucidating the hydrothermal ore-forming mechanism of high-purity quartz and artificial purification technologies.
Huang et al. (Thu,) studied this question.