Atomic structure and adhesion of the Nb(001)/α-Nb5Si3(001) interface: a first-principles study

Area of Science:

• Materials Science
• Computational Materials Science
• Surface Science

Background:

• Niobium silicides are advanced materials with potential applications in high-temperature environments.
• Understanding the interfacial properties of niobium and niobium silicide is crucial for predicting material performance and failure mechanisms.

Purpose of the Study:

• To investigate the surface and interface properties of Nb(001) and α-Nb5Si3(001) using density functional calculations.
• To determine the interfacial adhesion and identify potential sites for micro-crack initiation in Nb/α-Nb5Si3 systems.

Main Methods:

• Density functional theory (DFT) calculations were employed to model the Nb(001) and α-Nb5Si3(001) surfaces.
• Calculations included surface energy, cleavage energy, work of adhesion, and electronic structure analysis (density of states, Mulliken population, overlap population).

Main Results:

• The surface energy of Nb(001) was calculated as 2.25 J/m².
• Cleavage energies for bulk Nb5Si3 were found to be 5.103 J/m² (Nb-Si bonds) and 5.787 J/m² (Nb-NbSi bonds).
• The Nb(001)/α-Nb5Si3(001) interface exhibited the lowest work of adhesion compared to bulk Nb and Nb5Si3, with Nb-Si bonds identified as the weakest link.

Conclusions:

• The Nb(001)/α-Nb5Si3(001) interface is less stable than the individual bulk materials.
• The weaker Nb-Si bonds at the interface are the most probable sites for micro-crack generation under quasi-static stress along the [001] direction.
• Electronic structure analysis provides further details on bonding characteristics at the interface.