Structure, Energetics, and Impact of Screw Dislocations in Tricalcium Silicates

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• 作者：Rouzbeh Shahsavari ; Lei Tao and Lu Chen
• 刊名：Journal of the American Ceramic Society
• 出版年：2016
• 出版时间：July 2016
• 年：2016
• 卷：99
• 期：7
• 页码：2512-2520
• 全文大小：1781K
• ISSN：1551-2916

文摘

Understanding and quantifying the atomic structure, energetics, and the effect of defects on mechanics and reactivity of low symmetry oxides is an engineering challenge. This study focuses on atomistic analysis of screw dislocation in three thermodynamically reversible polymorphs of tricalcium silicate (Ca₃SiO₃), which is the key ingredient of cement. We employ molecular simulations to decode the interplay between the dislocation formation core energies, nonplanar core structures, displacement fields, disregistry functions, and Peierls stresses of tricalcium silicate polymorphs. By analyzing the core geometry at multiple scales, we found that the screw dislocations minimally impact the atomic bonds and angles at the vicinity of the Ca₃SiO₃ core dislocations, largely due to the sizeable channels and rigid body type relocation of atoms, which moderate most of the disturbances enforced by dislocations. Furthermore, we found that while the rhombohedral C3S (R-C3S) exhibits a relatively large core energy and core radius, the two monoclinic C3S structures (M3-C3S and MM-C3S) exhibited lower and almost identical core energies and core radii, likely due to the fact that they are two crystal realizations of the same polymorph. Finally, we discuss the implications of this work on brittleness and reactivity of cement crystals, and potential opportunities to better understand and modulate the grinding energy, reactivity, and mechanical properties of cement clinkers.