Designing highly incompressible transition metal nitrides: A new class of W_0.5Al_0.5N phases

Herein, we used first-principles calculations and the particle swarm optimization technique to predict a highly incompressible W_0.5Al_0.5N phase with the space group $R3¯m(166)$⁠. Our results reveal that this phase, which was characterized by a negative formation enthalpy, is thermodynamically and dynamically stable, as revealed by the absence of imaginary modes in the phonon spectra. Furthermore, its energetic stability at a pressure of 15 GPa indicates a feasible strategy for experimental synthesis. The high performance stems from the optimized octahedral coordination between N and W/Al. Additionally, the good elastic parameters with B_H of 310 GPa, G_H of 206 GPa, and H_V of 27 GPa confirm that it has preferable mechanical behaviors among the various W_0.5Al_0.5N phases and is even superior to those of the experimentally well-established NaCl-type phase. Based on the recently developed strain–stress method, it is shown that the ideal indentation strength of $R3¯m(166)$ is about 32.7 GPa in the (1 $1¯$ 0) [0 0 1] direction, which is in excellent agreement with estimated H_V. Therefore, our findings open the possibility for producing a new class of transition metal aluminum nitrides that have a broad range of applications.