AB-INITIO MOLECULAR DYNAMICS STUDY
ON CRYSTAL STRUCTURE OF BETA-DICALCIUM SILICATE
33rd Our World in Concrete and Structures (OWICs) - 2008
R Sakurada*, Akita National College of Technology, Japan
A K Singh, Rice University, U.S.A.
B Yakobson, Rice University, U.S.A.
M Uzawa, Taiheiyo Cement Co., Ltd., Japan
Y Kawazoe, Tohoku University, Japan
The crystal structures and hydraulic activities of ! and "- form dicalcium silicates (!-C2S, "-C2S) were analyzed by ab-initio calculation based on quantum mechanics. The mean distances less than 4 A to the neighboring Ca atoms for all of independent Ca atoms were calculated within unit cell. Ca-Ca mean distances are 3.56 A in !-C2S and 3.75 A in "-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 !-C2S substituted Ca(2) having eight-fold coordinates with Sr is unstable than !-C2S substituted Ca(1) having seven-fold coordinates with Sr.