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.