First-Principles Investigation of Interfacial Bonding, Stability, and Electronic Properties at the...

A systematic first-principles density functional theory (DFT) study was performed using the Perdew-Burke-Ernzerhof (PBE) generalized gradient approximation (GGA) functional combined with ultrasoft pseudopotentials (USPPs), as implemented in the CASTEP code. The PBE-GGA functional was chosen because it provides a well-balanced description of both metallic and covalent bonding characteristics at the Fe/Ti₃SiC₂ interface. To elucidate the interfacial bonding mechanisms and heterogeneous nucleation behavior of Ti₃SiC₂ particles in iron-based composites. The structural stability, work of adhesion, interfacial energy, and electronic properties of the Fe(111)/Ti₃SiC₂(0001) interface were comprehensively investigated. A total of eighteen interface models were constructed, encompassing six distinct Ti₃SiC₂(0001) terminations: C(TiC), C(TiSi), TiC(TiC), TiC(TiSi), TiSi, and Si, and three stacking sequences (OT, MT, and HCP). The results demonstrate that the C(TiC)-terminated interface with HCP stacking exhibits the highest work of adhesion (9.25 J·m^-2) and the lowest interfacial energy, thus representing the most thermodynamically stable configuration. Analysis of the partial density of states (PDOS) and charge density difference reveals that this exceptional stability originates from strong covalent bonding between Fe 3d and C 2p orbitals at the interface, accompanied by pronounced charge accumulation in the interfacial region. Furthermore, the work of adhesion of this interface substantially exceeds that of the fcc-Fe/fcc-Fe melt interface, confirming the high potency of Ti₃SiC₂ particles as heterogeneous nucleation substrates for Fe grains. These findings provide an atomistic framework for understanding the enhanced nucleation and robust interfacial cohesion observed in Fe/Ti₃SiC₂ composite coatings, and offer theoretical guidance for the design of advanced iron-based MAX phase composites.