Molecular dynamics simulations of the CaO-Al2O3-SiO2 system imply a different behaviour for the Si and Al atoms in the formation of aluminosilicate polyanions that is also influenced by their polymerization degree. Although both Si and Al in simulated systems prefer tetrahedral coordination by oxygen, the Al atoms are situated in the most branched positions so that they are bound mainly to bridging oxygen atoms while the Si atoms prefer bonding to non-bridging oxygen atoms. Increased polymerization is accompanied by the presence of 1 - 5% of TO5 groups (T = Si, Al). In the most polymerized system, about 7% of the oxygen atoms were observed to be bound to three T atoms.
