4. Conclusions
In summary, the structural stability, electronic, optical and mechanical properties of calcium carbonate hydrates are investigated in detail by first-principles calculations based on density functional theory in the present work. Firstly, the calculated phonon distribution curves of calcium carbonate hydrates are analyzed and find they are dynamic stability without no soft mode. Then, based on the analysis of the electronic structure and Mulliken’s overlap bond population of calcium carbonate hydrates, they have strong covalent-ionic character. What’s more, the optical properties of CaCO3·x H2O (x= 1/2, 1 and 6) are expounded in detail. It shows that dielectric function, reflectivity, conductivity, absorption, refractive index and loss function of CaCO3·x H2O (x= 1/2, 1 and 6) are decrease with the H2O increases. Finally, the elastic stiffness tensors of calcium carbonate hydrates are calculated. CaCO3·1/2H2O has the largest bulk modulus, shear modulus, Young’s modulus as 60.51 GPa, 36.56 GPa and 91.28 GPa, respectively. But CaCO3·1/2H2O has the highest Gibbs energy of reaction. Therefore, this work would be significant for not only expanding basic properties of the CaCO3 family but also understanding the further application of calcium carbonate hydrates in the future, such as biomineralization, geology, and industrial processes.