Insight into the effect of Mo and Re on mechanical and thermodynamic properties of NbSi2 based silicide

The improvement of overall performance of high-temperature materials is still a big challenge. By means of first-principles approach, in this work, we systematically investigate the effect of transition metals (TM=Mo and Re) on the strength and high-temperature thermodynamic properties of NbSi2 with C40 structure. The phonon dispersions, Debye temperature and heat capacity of NbSi2 with alloying elements are calculated in detail. We predict that alloying elements of Mo and Re are thermodynamically and dynamically stable. These alloying elements prefer to occupy the Si site in comparison to Nb site. We further find that the compression strength of NbSi2 with alloying element of Re is up to 15.3% in comparison to perfect NbSi2. Importantly, alloying elements at Si site result in brittle-to-ductile transition for NbSi2. The heat capacity of NbSi2 with alloying elements is slightly larger than that of NbSi2.