Investigating the Structural, Thermal, and Electronic Properties of the Zircon-Type ZrSiO4, ZrGeO4 and HfSiO4 Compounds

In the present study, the structural, thermal, and electronic properties of some important orthosilicate dielectrics, such as the ZrSiO 4 , ZrGeO 4 , and HfSiO 4 compounds, have been investigated theoretically with the use of first-principle calculations. We attribute the application of the modified Becke–Johnson exchange potential, which is basically an improvement over the local density approximation and the Perdew–Burke–Ernzerhof exchange–correlation functional, for a better description of the band gaps of the compounds. This resulted in a good agreement with our estimated values in comparison with the reported experimental data, specifically for the ZrSiO 4 , and HfSiO 4 compounds. Conversely, for the ZrGeO 4 compound, the calculated electronic band structure shows a direct band gap at the Γ point with the value of 5.79 eV. Furthermore, our evaluated thermal properties that are calculated by using the quasi-harmonic Debye model indicated that the volume variation with temperature is higher in the ZrGeO 4 compound as compared to both the ZrSiO 4 and HfSiO 4 compounds, which is ascribed to the difference between the electron shells of the Si and Ge atoms. Therefore, these results also indicate that while the entropy ( S ) and enthalpy ( U ) parameters increase monotonically, the free energy ( G ), in contrast, decreases monotonically with increasing temperature, respectively. Moreover, the pressure and temperature dependencies of the Debye temperature Θ, thermal expansion coefficient, and heat capacities C V were also predicted in our study.