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

Abstract

To further understand the structural behavior of Al3+ in the CaO‐SiO2‐Al2O3‐Li2O system melt, molecular dynamics simulations were used to analyze the microstructure of the melt under different basicity conditions. The results showed that the bond length of Al‐O was longer than that of Si‐O and was less stable than Si‐O. The stability of the [AlO4]5‐ tetrahedral structure was lower than that of the [SiO4]4‐ tetrahedral structure. With the increase of basicity, there was almost no effect on the Si‐O bond, but it caused the bond length of Al‐O to shorten and the bond length of Ca‐O to increase. At the same time, this led to the breakdown of complex aluminum‐oxygen ion clusters and the increase of the distance between O‐O atomic pairs. With the increase of basicity, the decrease in system energy promoted the gradual regularization of high‐coordinated Al ions under sufficient cation conditions, so that complex structures, such as O(Al,Al,Si) and O(Al,Al,Al), were transformed into simple structures, such as Al‐O‐Al, and the average value of the O‐Al‐O bond angle was closer to the ideal tetrahedral bond angle, and the proportion of tetrahedra increased. When the melt aggregation degree decreased, if two adjacent [AlO4]5‐ tetrahedra were connected by the same O, the distance between them would become larger, which also caused the average value of the Al‐O‐Al bond angle to gradually increase. The [SiO4]4‐ tetrahedra were more likely to be combined with [AlO4]5‐ tetrahedra. At the same time, the degree of decrease in Si‐O‐Al was not as great as that of Si‐O‐Si. CaO preferentially dissociates to provide O2‐, which in turn depolymerizes the Si‐O‐Si network structure to form non‐bridging oxygen Si‐O, and when basicity is sufficient, it will substantially depolymerize Si‐O‐Al to form Si‐O and Al‐O.This article is protected by copyright. All rights reserved.