Theoretical research on novel orthorhombic tungsten dinitride from first principles calculations

Tungsten nitrides have been intensely studied for technological applications owing to their unique mechanical, chemical, and thermal properties. Combining first-principles calculations with an unbiased structural searching method (CALYPSO), we uncovered a novel orthorhombic structure with a space group Cmc2₁ as the thermodynamically most stable phase for tungsten dinitride (WN₂) between 46-113 GPa. The computed elastic constants and phonons reveal that the Cmc2₁-WN₂ structure is dynamically stable at atmospheric pressure. Moreover, hardness calculations indicate that this structure is likely to become a hard material. Our current results may stimulate further experimental work on synthesizing these technologically important materials and improve the understanding of the pressure-induced phase transitions of other transition-metal light-element compounds.