A model study for the breaking of N2 from CNx within DFT
Résumé
A hypothetical CN2 structure was investigated as a model to study the release of N2 from the octahedral hole of 3D carbon based ultra hard compounds, which is the most important drawback in the attempts to synthesize ultra hard compounds like C3N4 and C11N4. Full structure relaxations using DFT methods led to a structure at the energy minimum showing a significantly enlarged N---N distance of 1.34 Å compared to the molecular N2 (1.09 Å). While for small volume changes a high hardness for CN2 of 405 GPa is calculated, we found that enlargements of the cell constant lead to the release of N2 that could be followed calculating the ELF and the charge transfer within the AIM theory. The whole procedure simulates an inverted “harpoon mechanism.