Title: Perspective on descriptors of mechanical behavior of cubic transition-metal carbides and nitrides

Abstract: Cubic rocksalt structured transition-metal carbides, nitrides, and related alloys (TMC/Ns) are attractive for a wide variety of applications, notably as hard, wear-resistant material. To-date, valence electron concentration (VEC) is used as a good indicator of stability and mechanical properties of these refractory compounds. In this perspective, we argue for the need for electronic descriptors beyond VEC to explain and predict the mechanical behavior of the cubic TMC/Ns. As such, we point out that descriptors that highlight differences between constituent have been underused, along with semi-empirical models of mechanical properties. Additionally, it appears promising to partition VEC into contribution to ionic, covalent, and metallic bonds and we suggest that such partition could provide more insight into predicting mechanical properties in the future.