Unraveling the structural, optoelectronic, and mechanical properties of calcium sulfate

Abstract

Although calcium sulfate (CaSO4) has been the subject of experimental research for many decades, several fundamental aspects of its physical behavior remain unresolved. In this work, we present a comprehensive theoretical investigation aimed at unraveling its structural, optoelectronic, and mechanical properties using first-principles calculations based on density functional theory. Structural optimization was performed using the density approximation, LDA, PBE, and PBEsol exchange–correlation functionals, which are suitable for accurately describing the structural, electronic, optical, and mechanical interactions within the system. To enhance the description of the electronic structure, we also employed the shielded HSE06 hybrid exchange–correlation functional, which resulted in a bandgap of Eg=7.271eV, in contrast to the value of Eg=6.044eV obtained with the semilocal PBEsol functional. The compound exhibited polarization-dependent optical absorption in the ultraviolet range, remaining practically isotropic. The estimated cohesive energy and phonon dispersion confirmed strong interatomic binding and high phonon frequencies. Furthermore, the values obtained for the elastic constants demonstrated that CaSO4 possesses high structural stability, suggesting its potential use in optoelectronic devices and as an insulating material in microelectronic systems. Overall, our findings provide a detailed understanding of the physical properties of CaSO4, consistent with the goal of unraveling its fundamental behavior.