First-Principles Modeling of Atomic Structure and Chemical and Optical Properties of β-C3N4

In our work, we report the results of first-principles modeling of optical and chemical properties of β-C3N4 in bulk (pristine and defected), surface, and nanoclusters. We demonstrate significant sensitivity of adsorption spectra of β-C3N4 to any kinds of disorder in atomic structure. Formation and passivation of the surface provides similar changes in optical properties. The value of the indirect bandgap depends on the chemical structure of the surface. The surface of the bulk crystal and nanocluster is chemically active and unavoidably passivated at ambient conditions. Partial oxidation of the surface of β-C3N4 provides decreasing of the bandgap. Functionalization of the active sites on the surface by monovalent species (hydrogen and fluorine) leads to vanishing of the bandgap in the case of (001) surface and changes the value of the bandgap in the case of nanoclusters. Results of our calculations also demonstrate the appearance of magnetic moments in hydrogenated and fluorinated (001) surface of β-C3N4.