Molecular Dynamics Analysis of the Structural Behavior of Aluminum Ion in the Slag of CaO–SiO2–Al2O3–Li2O System

In the study of CaO–SiO2–Al2O3–Li2O system slag, molecular dynamics simulations are performed to analyze the behavior of Al3+ at different alkalinities. The results show that the AlO bond length increases with increasing alkalinity and is unstable compared to the SiO bond. The [AlO4]5− tetrahedra are less stable than the [SiO4]4− tetrahedra. The higher the alkalinity, the shorter the AlO bonds and the longer the CaO bonds, thus destroying the aluminum‐oxygen ionophore. Increasing alkalinity converts complex structures into simpler ones, such as AlOAl, bringing the OAlO bond angles closer to the ideal tetrahedron. Reduced slag polymerization increases the distance between neighboring [AlO4]5− tetrahedra, thereby increasing the AlOAl bond angles. The [SiO4]4− tetrahedra prefer to bond with the [AlO4]5− tetrahedra. The change in SiOAl is less than that of SiOSi. The dissociation of CaO provides the O2−, which allows the depolymerization of SiOSi to form nonbridging oxygen SiO, whereas the depolymerization of SiOAl occurs when alkalinity is sufficient to form the SiO and AlO bonds. The [AlO4]5− tetrahedra are more likely to bond with [AlO4]5− tetrahedra than [AlO4]5− tetrahedra. To understand the structural behavior of Al3+ in the CaO–SiO2–Al2O3–Li2O slag system, molecular dynamics simulations are used to resolve the microstructure of Al ions under different alkalinity conditions. By studying the total energy of the slag system, the changes in bond length, coordination number, bond angle distribution, and oxygen species on the microstructure are explained.