Molecular dynamics study of the structural properties of calcium aluminosilicate slags with varying Al ₂O ₃/SiO ₂ ratios

Molecular dynamics simulation was explored to investigate the change of structure of calcium aluminosilicate slags with varying Al ₂O ₃/SiO ₂ ratios at a fixed CaO content. In practice the results of the study are relevant to the significant changes in slag structure caused by the changes in chemical composition during continuous casting of steels containing high amounts of dissolved aluminum. It was found that Q ⁴ tetrahedral species (tetrahedron with four bridging oxygens) increase while NBOs (non-bridging oxygen) decreases with increasing Al ₂O ₃/SiO ₂ mole ratio, suggesting that a more polymerized network was formed. The concentration of oxygen tricluster increased dramatically up to 24% with increasing Al ₂O ₃/SiO ₂ mole ratio, and the coordination number for Al (CN _Al-O) was also observed to increase from 4.02 for sample CAS1 to 4.11 for sample CAS11, suggesting that high coordination number of Al presents in the slag melt with the substitution of [AlO ₄] for [SiO ₄]. NBOs prefer to be coordinated with Si and Al tends to be localized in more polymerized environment as network intermediate phases. The degree of Al avoidance was calculated and the Al avoidance principle is applicable in the SiO ₂ rich regions.