Elastic constants and homogenized properties of two monoclinic structures (gypsum and tobermorite) were investigated by first-principles method. The gypsum (chemical formula of CaSO4•2H2O) is an evaporite mineral and a kind of hydration product of anhydrite. Besides, the 11 Å tobermorite model (chemical formula: Ca4Si6O14(OH)4·2H2O) as an initial configuration of C-S-H structure is commonly used. Elastic constants are calculated based on density functional theory (DFT), which can also contribute to provide information for investigating the stability, stiffness, brittleness, ductility, and anisotropy of gypsum and tobermorite polycrystals. In addition, based on elastic constants (13 independent constants) of the monoclinic gypsum crystal, the elastic properties of polycrystals are obtained. The bulk modulus B, shear modulus G, Young’s modulus E, and Poisson’s ration ν are derived. Therefore, it is fairly meaningful to study the elastic constants to understand the physical, chemical, and mechanical properties of two monoclinic structures. Elastic constants can be used as the measure criterion of the resistance of a crystal to an externally applied stress. The calculated parameters are all in excellent agreement with reference.
Part of the book: Density Functional Calculations