The search for efficient photocatalysts for sustainable hydrogen production has driven growing interest in barium titanate (BaTiO₃)-based materials, particularly through polymorph control, surface engineering, and nonmetal and transition-metal doping. In this work, we provide an atomic-scale understanding of structural modifications in nitrogen-, fluorine-, and rhodium-doped BaTiO₃ using Density Functional Theory (DFT), as well as pristine and fluorine-substituted BaTiO₃ using reactive force-field molecular dynamics (ReaxFF-MD) simulations. DFT results for pristine and doped tetragonal BaTiO₃, as well as pristine hexagonal BaTiO₃, reveal that nitrogen and rhodium substitutions enhance the covalent character of Ti-N and Rh-O bonds and promote the redistribution of electron density, as evidenced by noncovalent interaction (NCI) and critical point (QTAIM) analyses, whereas fluorine substitution leads to more ionic Ti-F bonding. ReaxFF-MD simulations of pristine and fluorine-substituted BaTiO₃ in contact with water molecules demonstrate that fluorine substitution suppresses interfacial O-H bond formation and promotes ordered molecular hydration layers near titanium sites, as reflected in bond statistics and radial distribution functions. This study provides molecular insights into the role of N, F, and Rh doping in BaTiO₃ using DFT, and the role of fluorine doping in BaTiO₃ at the water–solid interface using ReaxFF-MD simulations, demonstrating that this integrated computational approach provides a solid basis for the rational design of next-generation materials for energy-related applications. Direct calculations of photocatalytic activity, charge transfer rates, and ferroelectric polarization effects were not performed in this work and remain important directions for future study.

The interaction between calcium ions and hydrophobic silica-based material plays a critical role in understanding the durability and interfacial properties of protective coatings within concrete. In this study, Density Functional Theory (DFT) computations are utilized to investigate the interaction between calcium ions and model compounds within a silica-based hydrophobic material. These model compounds include 3-aminopropyltriethoxysilane (APTES), triethoxy(octyl)silane, Bisphenol A, and silicon dioxide. Geometry optimizations and electronic structure computations are carried out for these model compounds. The DFT computations are performed with the B3LYP/6-311++G(d,p) method with Grimme’s D3 correction. Molecular Electrostatic Potential (MEP), Reduced Density Gradient (RDG), and Non-Covalent Interaction (NCI) analyses are performed to investigate the charge distribution and intermolecular interactions. The results obtained from DFT computations show that calcium ion stabilization increases progressively from isolated organic modifiers to a complex silica-based material. While APTES, Bisphenol A, and triethoxy(octyl)silane make a contribution to calcium ion stabilization by weak to moderate intermolecular interactions, silicon dioxide shows the strongest interaction with calcium ions. Silicon dioxide seems to be the major contributor to calcium ion stabilization. However, the strong interaction between calcium ions and water points to hydration as a major competing effect.