Understanding of the Elastic Constants, Energetics, and Bonding in Dicalcium Silicate Using First-Principles Calculations

Atomistic scale modeling plays an increasingly important role in understanding the structural features and the structure-property relationships of materials. Herein, we systematically investigate the elastic constant, thermal conductivity, phonon dispersion, Raman signature, optical constant, and electronic band structure of dicalcium silicate (beta-Ca2SiO4 or C2S) performed with the norm-conserving pseudopotential method based on density functional theory. The obtained elastic constants are well consistent with the experimental and other theoretical values. The lattice thermal conductivity is about 1.0 W m(-1) K-1 at 300 K by using the simple Slack model, which manifests that C2S is more likely to be a desirable thermoelectric material. The specific heat capacity at a constant volume (C-v) is about 120.745 J mol(-1) K-1 at 300 K from the vibrational frequency. The thermal-state function of C2S such as vibrational entropy (S), vibrational enthalpy (H), and Helmholtz free energy (F) is calculated using the quasi-harmonic oscillator model. The simulated Raman peaks are in an excellent agreement with the experimental results. We demonstrate the significance of Coulombic interactions to understand the bonding feature and electron charge difference.