Venturing Further into the Field of 2D Materials and their Laminated Parent Phases

Abstract

The field of 2D materials is a relatively young and rapidly growing area within materials science, which is concerned with atomically thin states of matter. Because of their intrinsic 2D morphology, 2D materials have exceptionally high surface to weight or surface to volume ratio. This renders them excellent candidates for surface-sensitive applications such as catalysis and energy storage, which can aid us in the transition to a more sustainable society. 2D materials are also interesting because they show properties intrinsically different from those of their 3D counterparts, expanding the attainable property space within materials science. A 2D material can be synthesised by either a bottom-up or top-down approach. The focus here is on the latter, where the 2D material is derived by either mechanical exfoliation or selective etching of a 3D nanolaminated parent phase.A 3D laminate can typically be assigned to one of two types, depending on the type of interlayer bonding: van der Waals (vdW) or chemical bonding. In a vdW bonded phase, the constituent layers are kept together into their 3D form by rather weak vdW forces, while in the latter type, the layers are bound more strongly by chemical interactions (i.e., covalent, ionic and metallic bonds). The first 2D materials were derived from vdW-phases, which can be exfoliated by mechanical methods. In a chemically bound laminated phase, the inter layer bonding is stronger, and more complex methods are required for exfoliation of these phases into 2D. This thesis concerns the computational study and development of novel 2D materials through exploration of 3D nanolaminated structures, assessment of their phase stability, and potential for conversion into 2D. The 2D derivatives are in turn studied through prediction of dynamical stability, termination configuration, and evaluation of electronic properties.Paper III and IV each addresses a family of van der Waals structures. The family of 3D materials studied in Paper III was chosen because it was recently demonstrated as possible to use for derivation of so called 2D MXenes, while the 2D form of NbOCl 2 , from the family studied in Paper IV, has been shown to exhibit exciting optical properties. Both projects focus on identification of parent 3D materials, their exfoliation from 3D to i