Diffraction-pattern calculation and phase identification of hypothetical crystalline C3N4

In the present work we calculate x-ray powder-diffraction patterns and structure factors for electron diffraction of seven structures of hypothetical crystalline C3N4. Applying the same computational method, we calculate the x-ray powder-diffraction patterns of beta-Si3N4 and alpha-Si3N4 that match the experimental ones taken from the Joint Committee on Powder Diffraction Standards cards indicating very well the reliability of our computational programs. The discrepancy between calculated diffraction intensities and the experimental ones from synthesized C-N compounds indicates that all the claims regarding successful synthesis of crystalline beta-C3N4, alpha-C3N4, and defect zinc blende C3N4 are not convincing, at least from the paint of view of phase identification by the diffraction method. All the calculated patterns can be used as standard reference patterns in the future synthesis of C3N4. [S0163-1829(98)00541-4].