Effect of Fluorine on Melt Structure for CaO–SiO₂–CaF₂ and CaO–Al₂O₃–CaF₂ by Molecular Dynamics Simulations

抄録

The melt structure with fluorine addition has been investigated using molecular dynamics (MD) simulation for the CaO–SiO₂–CaF₂ and CaO–Al₂O₃–CaF₂ ternary slag system. By analyzing the coordination number of the network framework, the results indicate that the structure of Si–O tetrahedron is more stable than the structure of Al–O tetrahedron. F⁻ ions are dominantly coordinated with Ca²⁺, there is a dynamic equilibrium between Ca²⁺ and the coordination anions (O²⁻ and F⁻) in both systems, and the total coordination number (CN) is maintained between 6 and 7. The analysis of the distribution of oxygen types demonstrates the degree of polymerization (DOP) of network structure in CaO–SiO₂–CaF₂ system is lower than that in CaO–Al₂O₃–CaF₂ system. Although the addition of CaF₂ can lower the viscosity of both slag systems, the microscopic reasons for that are completely different: in CaO–SiO₂–CaF₂ system, CaF₂ actually acts as network diluent, and creates the space where particles can move longer. But in CaO–Al₂O₃–CaF₂ system, CaF₂ can depolymerize the network structure of the melt.