Atomic insight into the interfacial bonding and role of carbon atoms on β-SiC(1 1 1)/Al2MgC2(0 0 0 1): A first-principles study

Al₂MgC₂ may form on the interface of SiC/Mg composite, and as substrate of heterogeneous nucleation, Al₂MgC₂ could refine α-Mg grain. So, interface system SiC/Al₂MgC₂/Mg is interesting to be further clarified, while the study about SiC/Al₂MgC₂ is still insufficient. In present work, interfacial bonding on SiC(1 1 1)/Al₂MgC₂(0 0 0 1) and role of carbon atoms are investigated by using density functional theory (DFT) method. Considering different interfacial termination and stacking sites, totally 18 models are examined. Si/C-terminated and top-site stacked model (denoted as Si/C_top) is identified as the most stable one. Interfacial fracture toughness is predicted as critical stress intensity factor K_Ic^int = 2.34∼2.99 MPa•m^1/2. Interfacial bonding mostly contributes from carbon atoms, which behave as charge acceptors, and charge transfer between interfacial C-Si atoms is confirmed. Peaks in PDOS of interfacial C atoms shift towards negative side. Especially for C atom in SiC(1 1 1), shift from -1.33 eV to less than -2.9 eV, which generates stronger interfacial bonding. For C atom in Al₂MgC₂(0 0 0 1), new peak forms around -8.08 eV, and mainly from C-2p² orbital. Meanwhile, its s orbital peak negatively shifts from -9.71 eV to -11.61 eV. The interfacial Si-C covalent bonds are predominantly composed as hybridizations of C-2p² and Si-3s² around -8.1 eV, C-2p² and Si-3s² around -11.5 eV.