Effect of TiO2 Content on the Structure of CaO–SiO2–TiO2 System by Molecular Dynamics Simulation

The change of structure in the ternary system CaO–SiO2–TiO2 with TiO2 varying from 0 to 25% mole fraction at a fixed basicity of 0.8 was investigated by means of molecular dynamics simulation. The present simulation demonstrates that most Si is coordinated with 4 O within a tetrahedron while the majority of Ti with 6 O in an octahedron. With the addition of TiO2, the coordination number for Si (CNSi–O) changes from 4.12 to 4.03, while the CNTi–O varies from 5.83 to 5.52. The fraction of bridging oxygen (Si–O–Si) decreases resulting in the depolymerization of silicate structure and the Si–O–Ca is gradually replaced by Si–O–Ti with increasing TiO2 fraction. Two [TiO6] octahedrons are connected by two ways with the angles of Ti–O–Ti equaling to 100° and 140°, and the fraction of them are almost the same for sample with 10 mol-% TiO2 addition. The variation of network connectivity Qn of Si also agrees with the above conclusion. Thus, TiO2 is regarded as basic oxide which acts as modifier in this ternary system in terms of its structure within this system.