Clay mineral materials have attracted attention due to their many properties and applications. The applications of clay minerals are closely linked to their structure and composition. In this paper, we studied the electronic structure properties of kaolinite, muscovite, and montmorillonite crystals, which are classified as clay minerals, by using DFT-based ab initio packages VASP and the OLCAO. The aim of this work is to have a deep understanding of clay mineral materials, including electronic structure, bond strength, mechanical properties, and optical properties. It is worth mentioning that understanding these properties may help continually result in new and innovative clay products in several applications, such as in pharmaceutical applications using kaolinite for their potential in cancer treatment, muscovite used as insulators in electrical appliances, and engineering applications that use montmorillonite as a sealant. In addition, our results show that the role played by hydrogen bonds in O-H bonds has an impact on the hydration in these crystals. Based on calculated total bond order density, it is concluded that kaolinite is slightly more cohesive than montmorillonite, which is consistent with the calculated mechanical properties.

Inter‐granular glassy films (IGFs) are ubiquitous in structural ceramics and they play a critical role in defining their properties. The detailed origin of IGFs has been debated for decades with no firm conclusion. Herein, we report the result of quantum mechanical modeling on a realistic IGF model in β‐Si3N4 that unravels the fundamental reason for its development. We calculate the electronic structure, interatomic bonding, and mechanical properties using ab initio density functional theory with parallel calculations on crystalline β‐Si3N4, α‐Si3N4, γ‐Si3N4, and Si2N2O. The total bond order density—a quantum mechanical metric characterizing internal cohesion—of the IGF model and crystalline β‐Si3N4 are found to be identical. Detailed analysis shows that weakening of the bonds in the glassy film is compensated by strengthening of the interfacial bonds between the crystalline grain and the glassy layer. This provides a natural explanation for the ubiquitous existence of IGFs in silicon nitride and other structural ceramics. Moreover, the mechanical properties of this IGF model reveal its structural flexibility due to the presence of the less rigid glassy layer. This work demonstrates that high‐level computational modeling can now explain some of the most intriguing phenomena in nanoscale ceramic materials.

Montmorillonite clay (MMT) has been widely used in engineering and environmental applications as a landfill barrier and toxic waste repository due to its unique property as an expandable clay mineral that can absorb water easily. This absorption process rendered MMT to be highly exothermic due to electrostatic interactions among molecules and hydrogen bonds between surface atoms. A detailed study of a large supercell model of structural clay enables us to predict long-term nuclear waste storage. Herein, a large solvent MMT model with 4071 atoms is studied using ab initio density functional theory. The DFT calculation and analysis clarify the important issues, such as bond strength, solvation effect, elasticity, and seismic wave velocities. These results are compared to our previous study on crystalline MMT (dry). The solvated MMT has reduced shear modulus (G), bulk modulus (K), and Young’s modulus (E). We observe that the conduction band (CB) in the density of states (DOS) of solvated MMT model has a single, conspicuous peak at −8.5 eV. Moreover, the atom-resolved partial density of states (PDOS) summarizes the roles played by each atom in the DOS. These findings illuminate numerous potential sophisticated applications of MMT clay.