Insight into the structures,melting points,and mechanical properties of NbSi2 from first-principles calculations

Studies are carried out on the equilibrium structural, mechanical properties, and melting points of NbSi₂ with four ground-state crystal structures (C40, C11_b, C54, and C49) using first-principles approach. By means of the calculated formation enthalpies and phonon dispersion, it is found that these NbSi₂ phases are thermodynamically and dynamically stable. C54-NbSi₂ is uncovered to possess the lowest energy and formation enthalpy, implying that it is expected to be the most favorite structure for NbSi₂. The results of the calculated elastic constants reveal that four NbSi₂ phases are mechanically stable. We further find that the mechanical properties of C54-NbSi₂ are superior to those of the other NbSi₂ phases. The melting points of these NbSi₂ phases are calculated to examine their thermal stability. The elastic anisotropy is calculated and discussed using three patterns. The results prove that C54- and C40-NbSi₂ have good elastic isotropy, as confirmed by the given three-dimensional plots of elastic moduli. Analyzing the difference charge density and Mulliken overlap population provides the explanation about the relationship between bonding characteristics and mechanical properties.