Ab-initio Molecular Dynamics Study on Crystal Structure of Beta-dicalcium Silicate

The crystal structures and hydraulic activities of β and γform dicalcium silicates (β-C2S, γ-C2S) were analyzed by ab-initio calculation based on quantum mechanics. The mean distances less than 4 Å to the neighboring Ca atoms for all of independent Ca atoms were calculated within unit cell. Ca-Ca mean distances are 3.56 Å in β-C2S and 3.75 Å in γ-C2S. The shortening of Ca-Ca distance causes instability of a structure leading to a higher hydraulic activity. The interatomic bond lengths of the dicalcium silicates from the ab-initio calculations agree well with X-ray diffraction analysis. The substitution of Ca atom with Sr atom obtains an interest result that β-C2S substituted Ca(2) having eight-fold coordinates with Sr is unstable than β-C2S substituted Ca(1) having seven-fold coordinates with Sr.