Abstract: The microstructure of high-temperature xCaO-(1-x)Al₂O₃ melts was studied by the molecular
dynamics simulation. By comparing the positions of first peaks of partial radial distribution functions between Al and O, Ca and O, O and O, and the
coordination numbers of Al and Ca with the corresponding experimental data of X-ray diffraction and neutron scattering, which agree very well with each
other, the simulation is proved very successful. Based on the verification, it was found that Al playes the roll of network former in the calcium
aluminate melt. That’s to say, the average coordination number of Al is 4 and tetrahedron is the main structural unit in calcium aluminate just as
the action of Si in silicate melts. In the meantime, the distribution of 5 kinds of tetrahedrons Q_i was counted and then the regulation of the
changing microstructure of calcium aluminate melt following with the composition was analyzed. With the analysis of the number of next nearest
neighbor around the centering atom Al and the examination of the snapshot, 3-coordinated oxygen and charge-balanced bridging oxygen
were found to be the explanations of the phenomena of redundant charge and location of the cation Ca²⁺.

Key words: CaO.Al₂O₃ melt, microstructure, molecular dynamics