First-principles study on predicting the crystal structures, mechanical properties and electronic structures of HfCxN1-x

The crystal structures, mechanical properties and electronic structures of HfCxN1-x have been predicted by using evolutionary structure search followed by the first-principles calculations in this study. The crystal structures predicted indicate that there are 10 thermodynamic stable phases for HfCxN1-x, of which 8 are newly discovered crystal structures and 2 are already known. We investigated the mechanical properties, including the bulk modulus, shear modulus, Young's modulus, Poisson's ratio and Vickers hardness, of all 10 stable phases, and further established the relationship between such properties and the ratio of nitrogen to carbon content. Besides, the Fermi energy level and electronic density of states of these 10 stable phases are calculated as well, and the results reveal the fundamental reason why the mechanical properties change with the ratio of nitrogen to carbon. The predictions of this study agree well with both the experimental data and the previous theoretical evaluations.

Automated summary

This study predicts the crystal structures, mechanical properties, and electronic structures of HfCxN1-x using evolutionary structure search and first-principles calculations. It identifies 10 thermodynamic stable phases, 8 of which are newly discovered, and investigates the relationship between mechanical properties and the nitrogen to carbon ratio. The results also reveal the fundamental reason behind the change in mechanical properties with the ratio of nitrogen to carbon.