Theoretical study of structural characteristics, mechanical properties and electronic structure of metal (TM = V, Nb and Ta) silicides

• Structural stability of TMxSiy was explored by first principles calculations.
• Nb3Si2, Nb5Si4, Nb6Si5, NbSi and Ta3Si2 are proposed to be stable with lower ΔHf.
• The bulk modulus is following the order of Ta-Si > Nb-Si > V-Si at each stoichiometry.
• Mechanical and electronic properties of TMxSiy were analyzed in detail.

Using first-principles calculations, the crystal structure, mechanical property and electronic structure were investigated systematically for TM-Si (TM = V, Nb and Ta) systems. Pm  3¯n-V3Si, I4/mcm-V5Si3 and P6222-VSi2 for V-Si system, I4/mcm-Nb5Si3, P6222-NbSi2 for Nb-Si system, and P42/n-Ta3Si, I4/mcm-Ta2Si, I4/mcm-Ta5Si3, P6222-TaSi2 for Ta-Si system, are identified as thermodynamically stable structures, well consistent with previous theoretical and experimental reports. Stable P4/mbm-Nb3Si2, P41212-Nb5Si4, Ibam-Nb6Si5, Pnma-NbSi and P4/mbm-Ta3Si2 are proposed to be more likely realized in experiment because their formation enthalpies are close to convex-hull. The general order of bulk modulus is found to be Ta-Si > Nb-Si > V-Si at each stoichiometry. P6222-TMSi2 in each system shows the better mechanical properties. Both covalent bonding between Si-Si and Si-TM in TMSi2 are responsible for the structural stability and good mechanical property. The present study may shed light on better understanding of the phase relations in these transition metal silicides.