Effects of pressure on structural, mechanical, dynamics and thermal properties of Rankinite: Insights from first-principles calculations

Rankinite (3CaO center dot 2SiO(2), [C3S2]) is valued for its special properties in different environments. Understanding the properties of C3S2 is important for cement design. The lattice parameters, elastic constants and moduli, anisotropy, dynamical and thermal properties of C3S2 under 0-10 GPa was studied by first-principles method. The elastic properties, including bulk, shear and Young's moduli (B, G and E), Poisson's ratio v and hardness H-V, thermal conductivity k was calculated from the elastic moduli. The anisotropy of materials can be described by elastic anisotropy index, three-dimensional (3D) surface structure and elastic modulus projection. The results show that C3S2 has anisotropic elasticity, and the degree of anisotropy increases with the increase of pressure. The dynamic properties of C3S2 under different pressures are also calculated and analyzed. At last, the thermodynamic properties of C3S2 at different pressures are predicted and evaluated in detail.