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The chemical structure of an amorphous slag with blast furnace composition was investigated by means of molecular dynamics simulation. Our calculation suggested that the slag had a depolymerized network of SiO4 and AlO4 tetrahedra with interstitial cations, Ca2+ and Mg2+. The structural properties such as average coordination number obtained at 300 K were in good agreement with a recent NMR study, supporting the feasibility of the structure prediction by such simulation technique. At 1 873 K, the coordination numbers of the ions almost remained unchanged, while the intertetrahedral angles were found to be narrower, and the Qn distribution of AlO4 tetrahedra was slightly modified. The small amount but significant incorporation of MgO and Al2O3 influences the network connectivity, which should affect macroscopic properties such as viscosity.

In the cell model, a thermodynamic model of slag, the fractions of heterogeneous cation pairs are calculated which compose cells with an oxygen atom in between by the minimization of free energy of slag with energy parameters. On the other hand, by using NMR the fractions can be measured. Therefore, a new method can be proposed to evaluate the energy parameter values used in the cell model so that the calculated fractions in the slag with its minimum of free energy coincide with the measurement. The possibility of this evaluation method of energy parameter values was examined by the comparison of bridging oxygen/non-bridging oxygen (BO/NBO) ratio calculated by the cell model with energy parameter assessed elsewhere with measured BO/NBO ratio by NMR. The BO/NBO ratios of three SiO2–Al2O3–CaO slags with different basicities calculated by the use of cell model with energy parameter values assessed elsewhere were 42.5/57.5, 45/55 and 70/30, respectively. On the other hand, from 17OMAS spectrum and 27Al→17O CP/MAS spectrum of the same slags fully labeled and calcinated at 1600 centigrade degree, the ratios of BO/NBO in the slags were determined as 48.5/51.5, 42/58 and 76/24, respectively. This agreement supports the energy parameter values assessed elsewhere and gives a good expectation to the proposed method.