Optical properties of CaO, SiO2, Al2O3 and Fe2O3 cementitious oxides

We present a joint study of the optical properties of the relevant cementitious oxides CaO, SiO 2 , Al 2 O 3 , and Fe 2 O 3 , aimed at linking crystal structure, electronic properties, and optical response. Density functional theory (DFT) calculations were performed using both GGA and SCAN exchange–correlation functionals. Due to its superior accuracy, the SCAN ground-state was selected for GW and Bethe–Salpeter equation (BSE) calculations, used to correct the electronic structures and band gaps and to include electron–hole interactions. We show that the optical onset in the cement oxides is significantly influenced by the formation of strongly bound excitons. The results demonstrate that advanced methods beyond standard DFT, particularly the BSE approach, are essential for accurate prediction of the optical response of cementitious materials. Our findings provide a framework for understanding light–matter interactions in cement oxides and establish a computational foundation for the design of concrete-based composites with tailored optical and radiative properties. These insights have the potential to guide the development of advanced construction materials for passive energy management applications such as radiative cooling, in line with sustainable and energy-efficient building technologies. • First-principles study of the optical and excitonic properties of key cementitious oxides: CaO, SiO 2 , Al 2 O 3 , and Fe 2 O 3 . • Accurate electronic structure modeling using DFT requires GW and Bethe–Salpeter equation (BSE) methods, to predict optical absorption including exciton binding energies. • Delocalized, strongly bound excitons identified in CaO, SiO 2 , and Al 2 O 3 , modify the UV–visible part of the spectrum, which changes how much sunlight a certain oxide absorbs or reflects, being of potential interest for energy-harvesting or radiative cooling applications. • Fe 2 O 3 shows high visible absorption, a fact that limits its suitability for optical control in radiative cooling applications among these cement oxides.